  By means of density functional calculations the magnetic and electronic
properties and phase stabilities of the Heusler compounds Co$_2$MSi (with M=Ti,
V, Cr, Mn, Fe, Co, Ni) were investigated. Based on the calculated results we
predict the ferromagnetic phases of the compounds Co$_2$TiSi, Co$_2$VSi and
Co$_2$CrSi to be half-metals. Of particular interest is Co$_2$CrSi because of
its high density of majority spin states at Fermi energy in combination with a
reasonably high estimated Curie temperature of 747K. The compounds Co$_2$TiSi
and Co$_2$VSi are thermodynamically stable, whereas Co$_2$CrSi is a metastable
phase which might be stabilized by suitable experimental techniques.
