  The phase diagram of FeSi1-xGex, obtained from magnetic, thermal and
transport measurements on single crystals, shows a first-order transition from
a correlated electron semiconductor to a ferromagnetic metal at a critical
concentration, x ~ 0.25. The gap of the insulating phase strongly decreases
with x. The specific heat coefficient appears to track the density of states of
a Kondo insulator. The phase diagram is consistent with a correlation induced
insulator-metal transition in conjunction with disorder on the Si/Ge ligand
site.
