Recent Advances in the 5f-Relevant Electronic States and Unconventional Superconductivity of Actinide Compounds

Recent advances in the understanding of the 5 f -relevant electronic states and unconventional superconducting properties are reviewed in actinide compounds of UPd 2 Al 3 , UPt 3 , URu 2 Si 2 , UGe 2 , and PuRhGa 5 . These are based on the experimental results carried out on high-quality single crystal samples, including transuranium compounds, which were grown by using combined techniques. The paring state and the gap structure of these superconductors are discussed, especially for the corresponding Fermi surfaces which were clarified by the de Haas–van Alphen experiment and the energy band calculations. A detailed systematic study using the NQR/NMR spectroscopy reveals the d -wave superconductivity in PhRhGa 5 and the difference of magnetic excitations due to the difference of ground states in U-, Np-, and Pu-based AnTGa 5 (T: transition metal) compounds.