  The electronic and magnetic properties of Ti\raisebox{-.2ex}{\scriptsize
2}CoSi Heusler compound are investigated using density functional calculations.
The optimized lattice constant is found to be 6.030 A. The compound is a
half-metallic ferromagnet with an energy gap in minority spin channel of 0.652
eV at equilibrium lattice constant, which leads to a 100% spin-polarization.
The obtained total magnetic moment from spin-polarized calculations is 3.0
$\mu_{B}$ for values of lattice constants higher than 5.941 A. The
half-metallicity is spoiled for a compressed volume of 4%, suggesting a
possible application as pressure sensitive material.
