Possible observation of localized 4 f shell breakdown in praseodymium under pressure

A phase transition occurs in Pr at a pressure of 190 kbar and 300 K as seen from a precipitous resistance drop. In the low-P phase, the temperature dependence of the electrical resistivity is highly anomalous, the following features becoming more pronounced toward the transition. The temperature coefficient is extremely small between 300 K and 100 K. Below 50 K, the resistivity drops steeply. Both these features are well known for the γ and β phase of cerium. In contrast, the high-P phase exhibits a "normal", i.e. an almost linear temperature characteristic as also observed for Ce in the "collapsed" α phase. We suggest that the phase transition in Pr may turn out to be a counterpart of the γ→α transformation in Ce which is now understood as the delocalization of the 4 f¹ configuration into a 4 f band. © 1980 Springer-Verlag.