  The Fermi surface topology of a Weyl semimetal (WSM) depends strongly on the
position of the chemical potential. If it resides close to the band touching
points (Weyl nodes), as it does in TaAs, separate Fermi surfaces of opposite
chirality emerge, leading to novel phenomena such as the chiral magnetic
effect. If the chemical potential lies too far from the nodes, however, the
chiral Fermi surfaces merge into a single large Fermi surface with no net
chirality. This is realized in the WSM NbP, where the Weyl nodes lie far below
the Fermi energy and where the transport properties in low magnetic fields show
no evidence of chiral Fermi surfaces. Here we show that the behavior of NbP in
high magnetic fields is nonetheless dominated by the presence of the Weyl
nodes. Torque magnetometry up to 60 tesla reveals a change in the slope of
$\tau/B$ at the quantum limit B$^\star$ ($\approx 32\,\rm{T}$), where the
chemical potential enters the $n=0$ Landau level. Numerical simulations show
that this behaviour results from the magnetic field pulling the chemical
potential to the chiral $n=0$ Landau level belonging to the Weyl nodes. These
results show that high magnetic fields can uncover topological singularities in
the underlying band structure of a potential WSM, and can recover topologically
non-trivial experimental properties, even when the position of the chemical
potential precludes their observation in zero magnetic field.
