  Unidirectional transports have been observed in two-dimensional systems,
however, so far they have not been experimentally observed in three-dimensional
bulk materials. In this theoretical work we show that the recently discovered
Weyl materials provide a platform for unidirectional transports inside bulk
materials. With high experimental feasibility, a complex Dirac mass can be
generated and manipulated in the photonic Weyl crystals, creating
unidirectionally propagating modes observable in transmission experiments.
Possible realization in (electronic) Weyl semimetals is also studied. We show
in a lattice model that, with a short-range interaction, the desired form of
the Dirac mass can be spontaneously generated in a first-order transition.
