  The simplified bandstructure introduced by Mazurenko et al to model FeSi is
used to analyze the singlet semiconductor to ferromagnetic metal transition in
the isoelectronic isostructural alloys, FeSi$_{1-x}$Ge$_x$. The complex
bandstructure of the alloy is replaced by an alternating chain of doubly and
singly degenerate atoms to represent Fe and Si/Ge respectively. The
former(latter) form narrow(broad) bands with a substantial hybridization
between them. A substantial onsite repulsion including a Hund's rule coupling
is introduced on the Fe sites. The mean field phase diagram contains a first
order phase transition from the singlet semiconductor to a ferromagnetic metal
with increasing temperature and interaction strength similar to the alloys. The
analysis also reproduces the rapid rise of the spin susceptibility in the
semiconductor with a crossover to a Curie-Weiss form at higher temperatures.
Good agreement is found at zero temperature between the mean field and accurate
DMRG calculations.
