We report on the first synthesis of a Mn based ferromagnet on SixGe(1-x-y)Sny lattice matched on Ge with Sn content up to 15 %. The ferromagnetic layers were grown using interdiffusion of evaporated Mn and epitaxially grown SixGe(1-x-y)Sny. The Si to Sn ratio of the epitaxial layer is fixed to allow lattice matched growth on Ge. The possibility to grow the ferromagnetic layer directly on a semiconductor opens up the opportunity for large scale manufacturing using a selfaligned interdiffusion process. The compound exhibits a ferromagnetic phase for all samples studied. The observed Curie temperature remains around room temperature and shows no decisive trend with increasing Sn content. The samples show an increasing coercive field and decreasing saturation magnetization with increasing Sn content. This makes Mn-SixGe(1-x-y)Sny an interesting alternative to Mn5Ge3 as a ferromagnetically harder material for spintronics applications.