The electronic structure and structural stability of LaBiPt are studied by
using relativistic local-density energy band calculations. Total-energy cal
culations for three different atomic configurations within the MeAgAs-type
crystal structure show that the Pt atom is definitely on a unique site. For
the stable configuration, LaBiPt is semimetallic with hole and electron ca
rrier concentrations of 10(-4) e. Calculated hole Fermi surfaces have nearl
y a cubic shape, whose cross sections and their field-angle dependence are
in good agreement with recently observed Shubnikov-de Haas result. LaBiPt b
ecomes a zero-gap semiconductor without the spin-orbit coupling, indicating
that LaBiPt is a spin-orbit induced semimetal. The semimetallic nature ori
ginates mostly in BiPt and may be inherent in wider material systems like R
BiPt with rare-earth elements R.