*Citigroup bonus, Cayman Island investments to come up. WASHINGTON, Feb 13- The top Republican lawmaker vetting Jack Lew to serve as the U.S. treasury secretary on Wednesday zeroed in on the nominee's work as an executive at Citigroup as a possible conflict of interest for a job that would make him the nation's chief financial regulator.
*Citigroup bonus, Cayman Island investments to come up. WASHINGTON, Feb 13- Jack Lew, President Barack Obama's nominee to lead the U.S. Treasury Department, faces a grilling about a big bonus he received from Citigroup and his plans for the government's finances when he testifies before a Senate panel on Wednesday.