Intermediate valent metallic SmS and SmSe: A new puzzle

We have discovered that the R-T characteristic of so-called metallic SmS decreases with decreasing T at low temperatures for pressures exceeding≅20 kbar. This feature is reminiscent of a metal and in sharp contrast to the previously reported negative temperature coefficient at 10 and 20 kbar. The same fundamental change of the R-T dependence occurs in SmSe at ≅100 kbar. © 1981.