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The electronic structure of CeNiGe3 and YNiGe3 superconductors by ab initio calculations

Band structures of pressure-induced CeNiGe3 and exotic BCS-like YNiGe3 superconductors have been calculated employing the full-potential local-orbital code. Both the local density approximation (LDA) and LDA+U treatment of the exchange-correlation energy were used. The investigations were focused on differences between electronic properties of both compounds. Our results indicate that the Ce-based system exhibits higher density of states at the Fermi level, dominated by the Ce 4f states, in contrast to its non f-electron counterpart. The Fermi surface (FS) of each compound originates from three bands and consists of both holelike and electronlike sheets. The specific FS nesting properties of only CeNiGe3 enable an occurrence of spin fluctuations of a helicoidal antiferromagnetic character that may lead to unconventional pairing mechanism in this superconductor. In turn, the topology of the FS in YNiGe3 reveals a possibility of multi-band superconductivity, which can explain the observed anomalous jump at Tc in its specific heat.