We demonstrate a novel metal stanogermanide contact metallization process for high mobility germanium-tin (GeSn) channel MOSFETs. The multi-phase nickel-platinum stanogermanide [Ni(GeSn)+Pt-x(GeSn)(y)] contacts are formed by reacting Ni-Pt alloy with Ge0.947Sn0.053 alloy, which is epitaxially grown on Ge (100) substrate by solid source molecular beam epitaxy (MBE). Compared with nickel stanogermanide [Ni(GeSn)] contacts, the Pt-incorporated contacts, i.e. [Ni(GeSn)+Pt-x(GeSn)(y)], exhibit enhanced thermal stability in a wide range of formation temperatures and have superior surface morphology even after thermal processing. The proposed contacts are attractive for the integration in high mobility GeSn MOSFETs. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.014206esl] All rights reserved.