Three-dimensional condensed matter incarnations of Weyl fermions generically
have a tilted dispersion—in sharp contrast to their elusive high-energy
relatives where a tilt is forbidden by Lorentz invariance, and with the low-
energy excitations of two-dimensional graphene sheets where a tilt is
forbidden by either crystalline or particle-hole symmetry. Very recently, a
number of materials (MoTe2, LaAlGe, and WTe2) have been identified as hosts of
so-called type-II Weyl fermions whose dispersion is so strongly tilted that a
Fermi surface is formed, whereby the Weyl node becomes a singular point
connecting electron and hole pockets. We here predict that these systems have
remarkable properties in the presence of magnetic fields. Most saliently, we
show that the nature of the chiral anomaly depends crucially on the relative
angle between the applied field and the tilt, and that an inversion-asymmetric
overtilting creates an imbalance in the number of chiral modes with positive
and negative slopes. The field-selective anomaly gives a novel magneto-optical
resonance, providing an experimental way to detect concealed Weyl nodes
