Endoepitaxial growth of hexagonal-Fe13Ge8 islands on Cubic-Ge(001)

► Hexagonal Fe13Ge8 nanostructures have been grown on cubic Ge(001). ► Temperature-dependent shape evolution of Fe13Ge8 occurred via kinetic constraints. ► Nanostructures are formed by endoepitaxy and the mechanism is clarified accordingly. ► Endoepitaxy may predict nanowire formation in other heteroepitaxial systems.