The discovery of superconductivity at high pressure (albeit over a restricted range) in the ferromagnetic material UGe2 raised the possibility that bulk superconductivity might be found in other ferromagnets. The exact symmetry of the paired state and the dominant mechanism responsible for the pairing, however, remain unidentified. Meanwhile, the conjecture that superconductivity could occur more generally in ferromagnets has been fuelled by the recent observation of a low-temperature transition that suggests an onset of superconductivity in high-quality crystals of the itinerant-ferromagnet ZrZn2 (ref. 2), although the thermodynamic signature of this transition could not be detected. Here we show that the ferromagnet URhGe is superconducting at ambient pressure. In this case, we find the thermodynamic signature of the transition-its form is consistent with a superconducting pairing of a spin-triplet type, although further testing with cleaner samples is needed to confirm this. The combination of superconductivity and ferromagnetism may thus be more common and consequently more important than hitherto realized.

The pressure-temperature phase diagram of CeRhIn5 has been studied under high magnetic field by resistivity measurements. Clear signatures of a quantum critical point has been found at a critical pressure of pc ≈ 2.5 GPa. The field induced magnetic state in the superconducting state is stable up to the highest field. At pc the antiferromagnetic ground-state under high magnetic field collapses very rapidly. Clear signatures of pc are the strong enhancement of the resistivity in the normal state and of the inelastic scattering term. No clear T 2 temperature dependence could be found for pressures above Tc. From the analysis of the upper critical field within a strong coupling model we present the pressure dependence of the coupling parameter λ and the gyromagnetic ratio g. No signatures of a spatially modulated order parameter could be evidenced. A detailed comparison with the magnetic field-temperature phase diagram of CeCoIn5 is given. The comparison between CeRhIn5 and CeCoIn5 points out the importance to take into account the field dependence of the effective mass in the calculation of the superconducting upper critical field Hc2. It suggests also that when the magnetic critical field HM(0) becomes lower than Hc2(0), the persistence of a superconducting pseudo-gap may stick the antiferromagnetism to Hc2(0).

The pressure dependence of the critical temperature T c and upper critical field H c2 (T ) has been measured up to 19 GPa in the layered superconducting material 2H-NbSe 2 . T c (P ) has a maximum at 10.5 GPa, well above the pressure for the suppression of the CDW order. Using an effective two band model to fit H c2 (T ), we obtain the pressure dependence of the anisotropy in the electron phonon coupling and Fermi velocities, which reveals the peculiar interplay between CDW order, Fermi surface complexity and superconductivity in this system.

The thermal conductivity of the heavy fermion superconductor Pr(Os(4)Sb(12) was measured down to T(c)/40 throughout the vortex state. At lowest temperatures and for magnetic fields H approximately 0.07H(c2), already 40% of the normal state thermal conductivity is restored. This behavior (similar to that observed in MgB2) is a clear signature of multiband superconductivity in this compound.

The superconducting state of the heavy fermion PrOs4Sb12 is studied by heat transport measurements on a highly homogeneous single crystal exhibiting only one transition peak in the specific heat. The field and temperature dependence of the thermal conductivity confirm multiband superconductivity and point to fully open gaps on the whole Fermi surface.

We report measurements of the temperature dependence of both in-plane and out-of-plane penetration depths (lambda(a) and lambda(c), respectively) in 2H-NbSe2. Measurements were made with a radio-frequency tunnel diode oscillator circuit at temperatures down to 100 mK. Analysis of the anisotropic superfluid density shows that a reduced energy gap is located on one or more of the quasi-two-dimensional Nb Fermi surface sheets rather than on the Se sheet, in contrast with some previous reports. This result suggests that the gap structure is not simply related to the weak electron-phonon coupling on the Se sheet and is therefore important for microscopic models of anisotropic superconductivity in this compound.

We present new measurements of the specific heat of the heavy fermion superconductor PrOs4Sb12, on a sample which exhibits two sharp distinct anomalies at Tc1 = 1.89K and Tc2 = 1.72K. They are used to draw a precise magnetic field-temperature superconducting phase diagram of PrOs4Sb12 down to 350 mK. We discuss the superconducting phase diagram of PrOs4Sb12 and its possible relation with an unconventional superconducting order parameter. We give a detailed analysis of Hc2(T ), which shows paramagnetic limitation (a support for even parity pairing) and multiband effects.

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