  Holographic quantum matter exploits the AdS/CFT correspondence to study
systems in condensed matter physics. An example of these systems are strongly
correlated semimetals, which feature a rich phase diagram structure. In this
work, we present a holographic model for a Dirac semimetal in $2+1$ dimensions
that features a topological phase transition. Our construction relies on
deforming a relativistic UV fixed point with some relevant operators that
explicitly break rotations and some internal symmetries. The phase diagram for
different values of the relevant coupling constants is obtained. The different
phases are characterized by distinct dispersion relations for probe fermionic
modes in the AdS geometry. We find semi-metallic phases characterized by the
presence of Dirac cones and an insulating phase featuring a mass gap with a
mild anisotropy. Remarkably, we find as well an anisotropic semi-Dirac phase
characterized by a massless a fermionic excitation dispersing linearly in one
direction while quadratically in the other.
