By Andres Gonzalez and Rajesh Kumar Singh LONDON/CHICAGO, Sept 20 (Reuters) - General Electric Co GE.N 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 REP.MC, will take over on Jan. 1 and will be based in the United States, the memo said. Zingoni faces the challenge of navigating GE's power business through persistent supply chain and inflationary pressures.