In the course of searching for new systems, which exhibit nonsaturating and extremely large positive magnetoresistance, electronic structure, Fermi surface, and de Haas-van Alphen characteristics of the semimetallic YAs compound were studied using the all-electron full-potential linearized augmented-plane wave (FP-LAPW) approach in the framework of the generalized gradient approximation (GGA). In the scalar-relativistic calculation, the cubic symmetry splits fivefold degenerate Y-d orbital into low-energy threefold-degenerate t(2g) and twofold degenerate doublet e(1g) states at Gamma point around the Fermi energy. One of them, together with the threefold degenerate t(1u) character of As-p orbital, render the YAs semimetal with a topologically trivial band order and fairly low density of states at the Fermi level. Including spin-orbit (SO) coupling into the calculation leads to pronounced splitting of the t(1u) state and shifting the bands in the energy scale. Consequently, the determined four different 3-dimensional Fermi surface sheets of YAs consists of three concentric hole-like bands at G and one ellipsoidal electron-like sheet centred at the X points. In full accordance with the previous first-principles calculations for isostructural YSb and YBi, the calculated Fermi surface of YAs originates from fairly compensated multi-band electronic structures
