  Electron-hole mixing-induced fine structure in alkaline earth hexaborides
leads to lower energy (temperature) scales, and thus stronger tendency toward
an excitonic instability, than in their doped counterparts (viz.
Ca(1-x)La(x)B(6), x=0.005), which are high Curie temperature, small moment
ferromagnets. Comparison of Fermi surfaces and spectral distributions with de
Haas - van Alphen (dHvA), optical, transport, and tunneling data indicates that
SrB6 remains a fermionic semimetal down to (at least) 5 K, rather than forming
an excitonic condensate. For the doped system the Curie temperature is higher
than the degeneracy temperature.
