  The transition metal dipnictides TaAs2 , TaSb2 , NbAs2 and NbSb2 have
recently sparked interest for exhibiting giant magnetoresistance. While the
exact nature of magnetoresistance in these materials is still under active
investigation, there are experimental results indicating anisotropic negative
magnetoresistance. We study the effect of magnetic field on the band structure
topology of these materials by applying a Zeeman splitting. In the absence of
magnetic field, we find that the materials are weak topological insulators,
which is in agreement with previous studies. When the magnetic field is
applied, we find that type-II Weyl points form. This result is found first from
a symmetry argument, and then numerically for a k.p model of TaAs2 and a
tight-binding model of NbSb2. This effect can be of help in search for an
explanation of the anomalous magnetoresistance in these materials.
