Large Magnetoresistance and Nontrivial Berry Phase in Nb_3Sb Crystals with A15 Structure

Compounds with the A15 structure have attracted extensive attention due to their superconductivity and nontrivial topological band structures. We have successfully grown Nb_3Sb single crystals with the A15 structure and systematically measured the longitudinal resistivity, Hall resistivity and quantum oscillations in magnetization. Similar to other topological trivial/nontrivial semimetals, Nb_3Sb exhibits large magnetoresistance (MR) at low temperatures (717\%, 2 K and 9 T), unsaturating quadratic field dependence of MR and up-turn behavior in \rho_xx(T) curves under magnetic field, which is considered to result from a perfect hole-electron compensation, as evidenced by the Hall resistivity measurements. The nonzero Berry phase obtained from the de-Hass van Alphen (dHvA) oscillations demonstrates that Nb_3Sb is topologically nontrivial. These results indicate that Nb_3Sb superconductor is also a semimetal with large MR and nontrivial Berry phase. This indicates that Nb_3Sb may be another platform to search for the Majorana zero-energy mode.