METAL-INSULATOR-TRANSITION IN PRRU4P12 WITH SKUTTERUDITE STRUCTURE

The low temperature properties of PrRu4P12 and PrOs4P12 have been stud ied by means of electrical resistivity and magnetic susceptibility mea surements. The resistivity of PrRu4P12 decreases with decreasing tempe rature from room temperature to about 60 K, but increases sharply with decreasing temperature below 60 K. A metal-insulator transition is fo und at around 60 K. The susceptibility of the phosphide shows no disti nct anomaly at this temperature. No significant change in the powder x -ray diffraction pattern of PrRu4P12 is detected down to 10 K. The ano malous behavior may arise from a 4f instability of the Pr ion.