The structural and magnetic phase diagrams of Coa(1-x)MnaxGeb epitaxial films near the composition of Heusler alloy Co2MnGe have been studied using combinatorial molecular beam epitaxy techniques. Epitaxial growth on Ge (1 1 1) has been stabilized over nearly the entire composition range of the ternary system. Epitaxial constraints play an important role for the small number of observed structural phases. The variety of high-temperature magnetic properties, and the structural and chemical compatibilities with group IV elements make the ternary system promising for the science and applications of spintronics. (c) 2005 Elsevier B.V. All rights reserved.