By Andres Gonzalez and Rajesh Kumar Singh LONDON/CHICAGO (Reuters) – General Electric Co has hired Mavi Zingoni as head of its power unit, which comprises gas, steam and nuclear power businesses, according to an internal memo reviewed by Reuters on Tuesday. Zingoni, who served as executive managing director of client and low carbon generation business at Spanish energy group Repsol, will take over on Jan. 1 and will be based in the United States, the memo said. GE did not immediately respond to a request for comment. She joins at a time when the industrial conglomerate is gearing to split into…