T-Mobile USA Inc. Chief Executive Philipp Humm resigned Wednesday and will leave the company to reunite with his family in Europe. Mr. Humm will be replaced by Chief Operating Officer Jim Alling on an interim basis while a search for a successor is underway. Mr. Humm joined Deutsche Telekom AG (DTE.XE, DTEGY), which operates wireless service T-Mobile in the U.S, in 2005 and was initially responsible for the company's mobile business in Germany. His other roles in Europe include managing sales and service activities. He moved to the U.S. in May 2010. "Under his leadership the cost situation at T-Mobile USA has vastly improved and he led the company during a difficult phase regarding the planned merger with AT&T," Deutsche Telekom Chief Executive Rene Obermann said. AT&T Inc.'s (T) $39 billion bid for T-Mobile failed last year because of government resistance. T-Mobile has been looking to ramp up its network since the deal's collapse. In that deal, T-Mobile received $1 billion worth of spectrum, but analysts contend it likely needs more to remain competitive as rivals increase their use of fourth-generation network technology called long-term evolution, or LTE. Write to Chelsea Stevenson at chelsea.stevenson@dowjones.com