ANKARA, Turkey — Recep Tayyip Erdogan was sworn in on Monday for a five-year term under a new Constitution that gives Turkey’s president sweeping executive powers. He promptly named his son-in-law finance minister, an appointment that unsettled financial markets and raised new concerns about the concentration of so much power in one politician.
“We as Turkey, and the Turkish nation, are making a new start here in your presence,” Mr. Erdogan told hundreds of foreign leaders, dignitaries and party members gathered in the gardens of the presidential palace in Ankara, the capital. “We will make major moves in every area from macroeconomic balances to investments to make Turkey one of the 10 biggest economies of the world.”
Mr. Erdogan, who has been at the helm of Turkish politics since 2003, received a fresh mandate from voters last month on promises to make Turkey more efficient, and a great and strong state. As a result of a referendum he championed last year, the once-ceremonial presidency has vastly expanded powers.
Whether Mr. Erdogan can get a grip on the shaky Turkish economy is another matter. Government debt has exploded, fueled by borrowing for vast infrastructure projects, many of them built by contractors with ties to Mr. Erdogan and his allies. Turkey’s economy is still one of the world’s fastest growing, expanding at a rate of 7.4 percent last year, but the lira has fallen recently, a reflection of creditors’ and investors’ anxieties.
The currency fell further on Monday after Mr. Erdogan named his son-in-law, Berat Albayrak, a former energy minister, as treasury and finance minister. The new cabinet, announced late in the evening, was keenly awaited for an indication of what Mr. Erdogan plans with his newfound powers.
Many of the appointments were of bureaucrats; only four were of elected politicians. The foreign minister, Mevlut Cavusoglu, kept his position; the former army chief of staff, Hulusi Akar, was named defense minister; and an American-trained bureaucrat, Fuat Oktay, was named vice president.
Mr. Oktay had served as under secretary in the prime minister’s office, which was abolished with the transition to a presidential system.
“This means there will be more continuity than change,” Ozgur Unluhisarcikli, the director in Ankara of the German Marshall Fund of the United States, said before the announcement. “They will be implementers,” he added, “so he is taking things into his own hands.”
Mr. Erdogan has defended his constitutional change to introduce a strong presidential system — passed by referendum last year — as necessary for greater efficiency and a responsive government.
“The presidential government system is not coercive but a specific choice that the history directed us to,” he told his guests. “For the first time in history since Ottoman times, Turkey made its choice at a critical crossroads not by force of a military coup,” he said, “but with the free will of our nation.”
Critics warn the new presidential system will not solve Turkey’s problems, from growing economic strains to its bitterly divided politics.
“It is completely false that if we change the system problems will be solved,” said Murat Sevinc, a professor of constitutional law who writes a column for the newspaper Duvar. “They have built a system that is nongovernable, nonmanageable, whoever is elected.”
Few Western leaders were present — the only leader from the European Union was the president of Bulgaria — although a former chancellor of Germany, Gerhard Schröder, who has maintained close relations with Mr. Erdogan since his time in office, was present.
Prime Minister Dmitri A. Medvedev of Russia sat in the front row, alongside the presidents of Somalia, Sudan, Chad and Pakistan. The emir of Qatar was the only Arab leader present, and President Nicolás Maduro of Venezuela was the lone leader from the Americas. The United States was represented by Philip S. Kosnett, the chargé d’affaires at its embassy in Ankara.
The United States and European nations have criticized Mr. Erdogan’s growing authoritarianism in recent years, and in particular his harsh crackdown against political opponents since a failed coup in July 2016. Over 100,000 people have been arrested under a state of emergency since the coup, and 150,000 purged from their jobs.
Hours before his inauguration, Mr. Erdogan dashed off a decree ordering the firing of another 18,000 state employees, most of them members of the police and army, but also teachers and academicians.
The symbols of the day’s events were scrutinized for how they reflected on what is to come. Some of the celebrations were canceled out of respect for the 24 people killed when a train derailed in northwestern Turkey on Sunday evening.
Legislators from the main opposition parties — the Republican People’s Party and the Good Party, and the pro-Kurdish Democratic People’s Party — refused to stand as Mr. Erdogan took his oath before the newly elected Parliament. Mr. Erdogan entered the chamber to applause, but some boos rang out in the chamber as well.
The president remained stern faced throughout, even when waving to clapping supporters.
Mr. Erdogan won the presidential race with 52 percent of the vote, but his party failed to win a majority in Parliament and will work in alliance with the Nationalist Movement Party. Nearly half the Parliament — representing a population the size of Spain’s — remains opposed to Mr. Erdogan, said Soner Cagaptay, author of a book on Mr. Erdogan, “The Last Sultan.”
A clap of thunder sounded the moment after Mr. Erdogan took his oath, and rain descended upon the crowd gathering to celebrate the inauguration across town in the gardens of the presidential palace.
First, Mr. Erdogan paid his respects at the mausoleum of Mustafa Kemal Ataturk, the founder of the modern Turkish republic.
“Esteemed Ataturk,” he wrote in a visitors’ book. “I promise to go on strengthening the unity and fraternity of our nation, aggrandize our country, glorify our state.”
The gesture seemed intended to mollify opponents who have accused Mr. Erdogan of seeking to unravel the secular parliamentary republic that was Mr. Ataturk’s legacy.
Mr. Erdogan rode in a black car carpeted in red carnations, flanked by a mounted police escort to the presidential palace, arriving as Turkish artillery sounded a 21-gun salute.
On land that Mr. Ataturk had set aside for an experimental farm, Mr. Erdogan built a monumental palace four times the size of Versailles.
In regal procession, he walked the length of the palace gardens, with his wife, Emine, by his side, past a colorful honorary guard in medieval costumes. He greeted guests and supporters, and allowed himself a smile.
Follow Carlotta Gall on Twitter: @carlottagall