  Compounds with the A15 structure have attracted extensive attention due to
their superconductivity and nontrivial topological band structure. We have
successfully grown Nb$_3$Sb single crystals with a A15 structure and
systematically measured the longitudinal resistivity, Hall resistivity and
quantum oscillations in magnetization. Similar to other topological
trivial/nontrivial semimetals, Nb$_3$Sb, exhibits large magnetoresistance (MR)
at low temperatures (717$\%$, 2 K and 9 T), unsaturating quadratic field
dependence of MR and up-turn behavior in $\rho_{xx}$(\emph{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$_3$Sb is topologically nontrivial. These results indicate
that Nb$_{3}$Sb superconductor is also a semimetal with large MR and nontrivial
Berry phase, indicating that Nb$_{3}$Sb may be another platform to search for
Majorana zero-energy mode.
