  We show that the magnetic response of atomically thin materials with Dirac
spectrum and spin-orbit interactions can exhibit strong dependence on
electron-electron interactions. While graphene itself has a very small
spin-orbit coupling, various two-dimensional (2D) compounds "beyond graphene"
are good candidates to exhibit the strong interplay between spin-orbit and
Coulomb interactions. Materials in this class include dichalcogenides (such as
MoS$_2$ and WSe$_2$), silicene, germanene, as well as 2D topological insulators
described by the Kane-Mele model. We present a unified theory for their
in-plane magnetic field response leading to "anomalous", i.e. electron
interaction dependent transition moments. Our predictions can be potentially
used to construct unique magnetic probes with high sensitivity to electron
correlations.
