Fermi surface topology and electronic transport properties of chiral crystal NbGe2 with strong electron-phonon interaction

We report the electronic structures and transport properties of a chiral crystal NbGe2, which is a candidate for a coupled electron-phonon liquid. The electrical resistivity and thermoelectric power of NbGe2 exhibit clear differences compared to those of NbSi2 even though both niobium ditetrelides are isostructural and isoelectronic. We discuss the intriguing transport properties of NbGe2 based on a van Hove-type singularity in the density of states. The analysis of de Haas-van Alphen oscillations measured by the field modulation and magnetic torque methods reveals the detailed shape of the Fermi surface of NbGe2 by comparison with the results of energy band structure calculations using a local density approximation. The electron and hole Fermi surfaces of NbGe2 split into two because of the antisymmetric spin-orbit interaction. The temperature dependence of quantum oscillations indicates that the effective mass is isotropically enhanced in NbGe2 due to strong electron-phonon interaction.