Electrical resistivity and magnetization measurements on the heavy fermion superconductor PrOs4Sb12

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The filled skutterudite compound PrOs4Sb12, the first example of a Pr-based heavy fermion superconductor, displays superconductivity with Tc 1.85 K and has an effective mass m* 50 mₑ, where mₑ is the free electron mass. For magnetic fields above 4.5 T, sharp features in the normal state electrical resistivity, magnetization, specific heat, and thermal expansion data suggest the occurrence of a phase transition at high fields. This high field ordered phase in the normal state may originate from a combination of crystalline electric field enhanced Zeeman splitting and quadrupolar ordering. We present an investigation of the electrical resistivity and magnetization of PrOs4Sb12 as a function of temperature between 350 mK and 3.5 K and magnetic field up to 18 T. The data reveal a detailed phase boundary of the high field ordered phase as well as the lower critical field Hc₁ and the onset field of the peak effect in the superconducting state of PrOs4Sb12.