  We propose the creation of a two-dimensional topological semimetal in a
semiconductor artificial lattice with triangular symmetry. An in-plane magnetic
field drives a quantum phase transition between the topological insulating and
topological semimetal phases. The topological semimetal is characterized by
robust band touching points which carry quantized Berry flux and edge states
which terminate at the band touching points. The topological phase transition
is predicted to occur at magnetic fields $\sim 4\text{T}$ in high mobility GaAs
artificial lattices, and can be detected via the anomalous behaviour of the
edge conductance.
