  Weyl fermions can be created in materials with both time reversal and
inversion symmetry by applying a magnetic field, as evidenced by recent
measurements of anomalous negative magnetoresistance. Here, we do a thorough
analysis of the Weyl points in these materials: by enforcing crystal
symmetries, we classify the location and monopole charges of Weyl points
created by fields aligned with high-symmetry axes. The analysis applies
generally to materials with band inversion in the $T_d$, $D_{4h}$ and $D_{6h}$
point groups. For the $T_d$ point group, we find that Weyl nodes persist for
all directions of the magnetic field. Further, we compute the anomalous
magnetoresistance of field-created Weyl fermions in the semiclassical regime.
We find that the magnetoresistance can scale non-quadratically with magnetic
field, in contrast to materials with intrinsic Weyl nodes. Our results are
relevant to future experiments in the semi-classical regime.
