The pressure-volume relationship of stoichiometric TmSe has been investigated as a function of pressure up to 29 GPa by energy-dispersive x-ray-diffraction technique at room temperature. The results show a continuous valence change of Tm from the intermediate-valence state to a nearly trivalent state as the pressure reaches 5 GPa. The process of valence transition is, however, slowed down or briefly interrupted at around 2.5 GPa. A small lattice distortion apparently takes place at 10 GPa.

• Received 16 November 1981

DOI:https://doi.org/10.1103/PhysRevB.25.3841