  The combination of ferromagnetism and semiconducting behavior offers an
avenue for realizing novel spintronics and spin-enhanced thermoelectrics. Here
we demonstrate the synthesis of doped and nanocomposite half Heusler
Fe$_{1+x}$VSb films by molecular beam epitaxy. For dilute excess Fe ($x <
0.1$), we observe a decrease in the Hall electron concentration and no
secondary phases in X-ray diffraction, consistent with Fe doping into FeVSb.
Magnetotransport measurements suggest weak ferromagnetism that onsets at a
temperature of $T_{c} \approx$ 5K. For higher Fe content ($x > 0.1$),
ferromagnetic Fe nanostructures precipitate from the semiconducting FeVSb
matrix. The Fe/FeVSb interfaces are epitaxial, as observed by transmission
electron microscopy and X-ray diffraction. Magnetotransport measurements
suggest proximity-induced magnetism in the FeVSb, from the Fe/FeVSb interfaces,
at an onset temperature of $T_{c} \approx$ 20K.
