  We present a microscopic theory of diffusive magnetotransport in Weyl metals
and clarify its relation to chiral anomaly. We derive coupled diffusion
equations for the total and axial charge densities and show that chiral anomaly
manifests as a magnetic-field-induced coupling between them. We demonstrate
that a universal experimentally-observable consequence of this coupling in
magnetotransport in Weyl metals is a quadratic negative magnetoresistance,
which will dominate all other contributions to magnetoresistance under certain
conditions.
