  Magnetotransport provides key experimental signatures in Weyl semimetals. The
longitudinal magnetoresistance is linked to the chiral anomaly and the
transversal magnetoresistance to the dominant charge relaxation mechanism.
Axial magnetic fields that act with opposite sign on opposite chiralities
facilitate new transport experiments that probe the low-energy Weyl nodes. As
recently realized, these axial fields can be achieved by straining samples or
adding inhomogeneities to them. Here, we identify a robust signature of axial
magnetic fields: an anomalous scaling of the conductance in the diffusive
ultraquantum regime. In particular, we demonstrate that the longitudinal
conductivity in the ultraquantum regime of a disordered Weyl semimetal
subjected to an axial magnetic field increases with both the field strength and
sample width due to a spatial separation of charge carriers. We contrast axial
magnetic with real magnetic fields to clearly distinguish the different
behavior of the conductance. Our results rely on numerical tight-binding
simulations and are supported by analytical arguments. We argue that the
spatial separation of charge carriers can be used for directed currents in
microstructured electronic devices.
