  Weyl fermions possess the property of spin-momentum locking: the expectation
value of the spin is parallel or antiparallel to the momentum at any given
point in the Brillouin zone in the vicinity of a Weyl node. This is a direct
consequence of the fact that Weyl nodes are monopoles of the Berry curvature,
and in this sense an expression of the nontrivial Weyl electronic structure
topology. Thanks to this property, an isolated Weyl node produces a large spin
accumulation in response to a charge current, $\hbar/2$ per electron, similar
to surface states of time-reversal invariant topological insulators. However,
in bulk Weyl semimetals, the nodes must occur in pairs of opposite chirality
and, when the nodes are at the same energy, the effect cancels out. Here we
show that this cancellation is avoided in chiral semimetals, in which Weyl
nodes of opposite chirality occur at different energies due to broken mirror
symmetry. We find that the spin accumulation is maximized when the Fermi energy
coincides with one of the nodes in a pair and reaches the same value as for an
isolated node in this case. Moreover, we demonstrate the existence of a
distinct magnetoresistance mechanism, closely related to this current-induced
spin accumulation.
