WASHINGTON (AP) -- Treasury Secretary nominee Jacob Lew is facing sharp questions from Republicans over his tenure at Citigroup (NYSE:C) during the financial crisis and a nearly $1 million bonus he received while the bank was being bailed out by taxpayers.

Lew joined Citi in 2006 and became chief operating officer for its alternative investments unit in January 2008. He held the position during the peak of the financial crisis, when Citi received a $45 billion bailout from the federal government.

Lew's unit had been criticized for making risky investments that imploded during the crisis. But Lew said during a Senate Finance Committee hearing that he did not make investment decisions in his job.

He received a $940,000 bonus in early 2009, shortly before he left to join the Obama administration.