Electronic band structure and fermi surface of heavy-fermion neptunium superconductor NpPd5Al2

Electronic band structure calculations were carried out for a new neptunium superconductor NpPd5Al2 using a relativistic linear-augmented plane wave method within a local density approximation. The Fermi energy in the band structure is found to be located just on the 5f-bands of the j = 5/2 state with the extremely narrow band width and therefore the theoretical electronic specific heat coefficient gamma b is extremely large, being gamma b = 74.0 mJ/(K-2.mol), which is compared to gamma = 390 mJ/(K-2.mol) estimated experimentally. NpPd5Al2 is an uncompensated metal. The main electron Fermi surface corresponds to a doughnut-like flat Fermi surface centered at the T point which is connected with cylindrical Fermi surfaces elongated along the X-W-P line.