BUENOS AIRES — As Argentina absorbs the shock from a sharp plunge in its currency, President Cristina Fernández de Kirchner’s mercurial young economy minister, Axel Kicillof, a scholar with rockabilly-style sideburns and an aversion to business suits, is emerging as the face of policy shifts that are sending tremors through financial markets around the developing world.

Mr. Kicillof, 42, is wielding greater influence over an array of areas, from Argentina’s oil industry to the government’s attempts to slow capital flight and improve relations with international creditors, as Mrs. Kirchner remains largely absent from the public eye after undergoing surgery in October to drain a blood clot near her brain.

The rise of Mr. Kicillof, whose writings use Marxist concepts to interpret the work of the British economist John Maynard Keynes, points to efforts by the authorities to assert greater state control over Argentina’s economy at a time when growth is slowing significantly and inflation is soaring.

“He’s the strongest economy minister Argentina has had in a decade,” said Ezequiel Burgo, the author of “The Believer,” a book about Mr. Kicillof. “He’s confrontational, outwardly self-confident and sometimes perceived as being arrogant, which of course makes him stand out at a time like this.”