Resistivity plateau and negative magnetoresistance in the topological semimetal TaSb2

We report the discovery of a topological semimetal, TaSb2, which crystallizes in a base-centered monoclinic, centrosymmetric structure. The compound undergoes a metal-insulator-like transition under magnetic field and exhibits a clear resistivity plateau below T-c = 13 K. The ultrahigh carrier mobility and extreme large magnetoresistance for longitudinal resistivity are observed at low temperatures in addition to a quantum oscillation behavior with nontrivial Berry phases. Moreover, the negative magnetoresistance is observed when the applied field is parallel to the current direction up to 9 T. The Hall resistivity shows the nearly linear field dependence suggestive of electron-hole noncompensation behavior. These findings uncover a materials basis represented by TaSb2 as a platform of topological materials for future theoretical and experimental investigations.