Fermi surface topology and negative longitudinal magnetoresistance observed in the semimetal NbAs2

We report transverse and longitudinal magnetotransport properties of NbAs2 single crystals. Attributing to the electron-hole compensation, nonsaturating large transverse magnetoresistance reaches up to 8000 at 9 T at 1.8 K with mobility around 1 to 2 m(2) V-1 S-1. We present a thorough study of angular-dependent Shubnikov-de Haas (SdH) quantum oscillations of NbAs2. Three distinct oscillation frequencies are identified. First-principles calculations reveal four types of Fermi-surface pockets: electron alpha pocket, hole beta pocket, hole gamma pocket, and small electron delta pocket. Although the angular dependence of alpha, beta, and delta agree well with the SdH data, gamma pocket is missing in SdH. Negative longitudinal magnetoresistance is observed which may be linked to novel topological states in this material, although systematic study is necessary to ascertain its origin.