  Weyl semimetals are gapless three-dimensional topological materials where two
bands touch at even number of points in the Brillouin zone. In this work we
study a zincblende lattice model realizing a time-reversal invariant Weyl
semimetal. The bulk dynamics is decribed by twelve helical Weyl nodes. Surface
states form a peculiar quasi two-dimensional helical metal fundamentally
different from the Dirac form typical for topological insulators. Allowed
direction of velocity and spin of low-energy surface excitations are locked to
the cubic symmetry axes. The studied system illustrates general properties of
surface states in systems with common crystal symmetries.
