Superconductivity of the filled skuterrudite : Phase diagram and characterisations

We present a precise ( H – T ) phase diagram of the double superconducting transition in the specific heat of the heavy fermion superconductor PrOs 4 Sb 12 , down to 350 mK, on a sample which exhibits two sharp distinct anomalies at T c 1 = 1.89 K and T c 2 = 1.72 K . Comparison with an existing phase diagram based on transport measurements will be reviewed. The intrinsic or extrinsic nature of this double transition is discussed in light of some characterisations of the superconducting transition of different samples and with respect to the historical case of UPt 3 . Finally, we give a detailed analysis of H c 2 which shows the importance of the multiband character of the electronic structure of PrOs 4 Sb 12 and gives strong support to an even parity order parameter.