  We numerically study the three-dimensional (3D) quantum Hall effect (QHE) and
magnetothermoelectric transport of Weyl semimetals in the presence of disorder.
We obtain a bulk picture that the exotic 3D QHE emerges in a finite range of
Fermi energy near the Weyl points determined by the gap between the $n=-1$ and
$n=1$ Landau levels (LLs). The quantized Hall conductivity is attributable to
the chiral zeroth LLs traversing the gap, and is robust against disorder
scattering for an intermediate number of layers in the direction of the
magnetic field. Moreover, we predict several interesting characteristic
features of the thermoelectric transport coefficients in the 3D QHE regime,
which can be probed experimentally. This may open an avenue for exploring Weyl
physics in topological materials.
