After more than nine years in Citigroup Inc.'s economics research group, most recently as chief economist, Lewis Alexander is leaving the firm to return to Washington. Alexander (pictured) is joining the U.S. Treasury to work on domestic financial issues, counseling Secretary Timothy Geithner. Before joining Citi in 1999, he worked in the division of international finance of the Federal Reserve Board. He was also the Commerce Department's chief economist.

Citi's head of investment research, Andrew Pitt, wrote in a memo that Don Hanna, deputy chief economist, will continue to coordinate Citi's economics research globally. He said the firm will announce an enhanced structure for global economics coverage.

Paul Raphael, head of investment banking for Asia-Pacific, is leaving Credit Suisse Group to pursue new opportunities. He previously led the investment banking franchise across Europe, the Middle East and Africa and was co-head of the global markets solutions group and head of Central Eastern Europe Middle East and Africa.

Vikram Malhotra and Helman Sitohang become co-heads of investment banking for Asia-Pacific. They are also co-heads of the global markets solutions group. They report regionally to Kai Nargolwala, CEO, Asia-Pacific, and globally to Jim Amine and Marc Granetz, global co-heads of investment banking.

Chris Hughes, co-founder of social networking Web site Facebook Inc., joined venture capital firm General Catalyst Partners as an entrepreneur-in-residence. Hughes was director of online organizing for President Barack Obama's presidential campaign through political social networking site My.BarackObama.com. The 25-year-old will split his time between New York and Cambridge, Mass.

U.K. private equity firm Terra Firma Capital Partners Ltd. is separating its chairman and CEO role. After seven years in that role, Guy Hands will become group chairman and chief investment officer, handing over day-to-day responsibility for Terra Firma's operations to Tim Pryce, who becomes CEO. Pryce, who worked with Hands at Nomura Holdings Inc., was a founder member of Terra Firma and is a member of the investment advisory and remuneration committees. He was also general counsel.

Terra Firma recently took a £1.3 billion ($1.7 billion) write-down on its acquisition of EMI Group Ltd.

Private Capital Management LP co-founder Bruce Sherman is retiring on March 31. Recent bets on the U.S. media industry and investments in Bear Stearns Cos. have hurt the Legg Mason Inc. unit. Last year, Sherman gave the CEO role to president Gregg Powers.

Separately, Legg Mason appointed Jeffrey Nattans as senior vice president, head of specialized managers. He will report to chairman and CEO Mark Fetting. Nattans joined the firm from Goldman, Sachs & Co. in New York in 2006 as a managing director in the administrative management group, focusing on corporate strategy and mergers and acquisitions.

Also, Legg Mason named Alan Magleby as managing director, head of investor relations and corporate communications. Magleby joins from Washington Mutual Inc., where he was senior vice president, investor relations, since 2004.

Barclays plc appointed Izzat Nuseibeh as CEO of its investment banking and investment management business in Qatar. He reports to Soha Nashaat, CEO of Barclays Wealth, Middle East and North Africa. Nuseibeh spent the last five years at Credit Suisse Group as senior executive serving the Abu Dhabi and Doha offices. Before that, he spent 10 years at Deutsche Bank AG, based in Abu Dhabi.

In New York, consumer products banker Kenneth Wasik joined Stephens Inc. as a managing director in corporate finance, responsible for sourcing underwriting and merger and acquisition advisory work.

Wasik was a managing director at Jefferies & Co., where he headed the consumer products team. He also led the consumer products group at Houlihan, Lokey, Howard & Zukin Inc. and was a banker at UBS.

Garrett Baker was named president of Waller Capital Partners LLC, an independent investment bank focused on the media, communications and information industries. Baker joined the firm in 1998, after working in the merger and acquisition and restructuring groups at Bear, Stearns & Co. He has led Waller's cable efforts since 2003.

The firm also promoted Jeffrey Brandon to managing director, Kenneth Clausman to director, and Michael Cohen and Christopher Erwin to associates. Brandon joined Waller Capital in 2006 from Bear Stearns, where he was an investment banker in the media and entertainment group. Formerly, he was an attorney with Latham & Watkins LLP and began his career in 1990 as a litigator with the U.S. Federal Trade Commission.

Last week, the firm hired Brian Stengel as a managing director to lead the digital media practice, based in New York. Stengel was previously a senior investment banker at Morgan Stanley, where he worked with private equity firms and their portfolio companies on leveraged acquisitions, debt and equity financings and principal investing with a focus on technology, media and telecoms.

Stengel previously worked at Goldman, Sachs & Co., J.P. Morgan Chase & Co. and venture capital fund eColony.