  We report a topological semimetal W2As3 with a space group C2/m. Based on the
first-principles calculations, band crossings are partially gapped when
spin-orbit coupling is included. The Z2 indices at the electron filling are
[1;111], characterizing a strong topological insulator and topological surface
states. From the magnetotransport measurements, nearly quadratic field
dependence of magnetoresistance (MR) (B || [200]) at 3 K indicates an
electron-hole compensated compound whose longitudinal MR reaches 115 at 3 K and
15 T. In addition, multiband features are detected from the high-magnetic-field
Shubnikov-de Haas (SdH) oscillation, Hall resistivity, and band calculations. A
nontrivial pi Berry's phase is obtained, suggesting the topological feature of
this material. A two- band model can fit well the conductivity and Hall
coefficient. Our experiments manifest that the transport properties of W2As3
are in good agreement with the theoretical calculations.
