  We study odd viscosity in a holographic model of a Weyl semimetal. The model
is characterised by a quantum phase transition from a topological semimetal to
a trivial semimetal state. Since the model is axisymmetric in three spatial
dimensions there are two independent odd viscosities. Both odd viscosity
coefficients are non-vanishing in the quantum critical region and non-zero only
due to the mixed axial gravitational anomaly. It is therefore a novel example
in which the mixed axial gravitational anomaly gives rise to a transport
coefficient at first order in derivatives at finite temperature. We also
compute anisotropic shear viscosities and show that one of them violates the
KSS bound. In the quantum critical region, the physics of viscosities as well
as conductivities is governed by the quantum critical point.
