The pressure variation of resistivity and optical absorption in SmTe has been studied. A continuous pressure-induced semiconductor-to-metal transition is observed, which we ascribe to the promotion of electrons from the $4f$ level into the conduction band as the gap between them shrinks with pressure and finally vanishes. The gap deduced from the saturation resistivity ratio $\frac{\rho {\mathrm{}\left(P\right)\mathrm{}}_{\mathrm{sat}}}{\rho \mathrm{}\left(0\right)\mathrm{}}$ is in good agreement with the gap of 0.62 ± 0.02 eV obtained from infrared absorption data.

• Received 24 June 1970

DOI:https://doi.org/10.1103/PhysRevLett.25.368