Pressure Temperature Behavior of the Electronic Transitions in Sm4Bi3

The first-order valence transition boundary in Sm4Bi3 has a large positive dT/dP and terminates at a critical point above 700°K and 28 kbar. An anomalous decrease in resistance near 273°K at ambient pressure is observed, and this is attributed to a change of state from the inhomogeneously mixed to a homogeneously mixed valence state. This phase boundary has a negative slope and intersects the first-order valence transition boundary at a triple point near 225°K and 25 kbar. In the high pressure phase all the Sm ions are in the fully trivalent state.