With extensive experience in project structuring, Fermín regularly participates in projects in the energy, mining, and construction sectors, as well as in debt refinancing. He also provides advice on financial, exchange, and stock markets, acting before the Argentine Central Bank, the National Securities Commission, and various securities markets. Fermín is frequently called upon to participate in mergers and acquisitions operations.

During 2007 and 2008 Fermín worked as a foreign associate for Simpson Thacher & Bartlett. In 2008, he also worked as an in-house attorney for Merrill Lynch, advising the Credit Principal Group on credit and investment operations in Latin America, working for teams in New York, São Paulo, Mexico City, and Buenos Aires.

Fermín is a member of the International Bar Association and the Committee of Bank Lawyers of the Argentine Republic. He is a professor in the Master of Finance program at the Torcuato Di Tella Business School in Buenos Aires.