Abstract
Measurements of the pressure dependence of the Hall coefficient and conductivity of TiS2 indicate that TiS2 is an extrinsic semiconductor. The strong temperature dependence of the conductivity is matched by a strong pressure dependence that is consistent with electron-phonon scattering. In contrast, TiSe2 is a semimetal, with a strongly pressure dependent p-d band overlap. The transition temperature of the structural phase transition in TiSe2 falls at -1.2K kbar-1.