We measured the electrical resistivity, specific heat, magnetic susceptibility and magnetization in the first Np-based superconductor NpPd 5Al2 with the tetragonal crystal structure. NpPd 5Al2 is a paramagnet and becomes the superconductivity at Tc = 4.9 K. The large electronic specific heat coefficient of γ = 200 mJ/K2mol at Tc indicates that NpPd 5Al2 is a heavy fermion superconductor. The upper critical field Hc2 is large and highly anisotropic: Hc2(0) = 37 kOe for H ∥  and Hc2(0) = 143 kOe for H ∥ . Although the initial slope of Hc2 at Tc is very large, Hc2 is strongly suppressed against the magnetic field for both field direction, indicating the existence of strong Pauli paramagnetic effect. Furthermore, the magnetization curve shows the step-like behaviors at H c2, corresponding to the first order transition. The d-wave superconductivity with the spin-singlet state is most likely realized in NpPd5Al2.
- Heavy-fermion superconductivity
- Paramagnetic effect
- non-Fermi liquid
ASJC Scopus subject areas
- Physics and Astronomy(all)