  Weyl semimetals have sparked intense research interest, but experimental work
has been limited to the TaAs family of compounds. Recently, a number of
theoretical works have predicted that compounds in the Mo$_x$W$_{1-x}$Te$_2$
series are Weyl semimetals. Such proposals are particularly exciting because
Mo$_x$W$_{1-x}$Te$_2$ has a quasi two-dimensional crystal structure well-suited
to many transport experiments, while WTe$_2$ and MoTe$_2$ have already been the
subject of numerous proposals for device applications. However, with available
ARPES techniques it is challenging to demonstrate a Weyl semimetal in
Mo$_x$W$_{1-x}$Te$_2$. According to the predictions, the Weyl points are above
the Fermi level, the system approaches two critical points as a function of
doping, there are many irrelevant bulk bands, the Fermi arcs are nearly
degenerate with bulk bands and the bulk band gap is small. Here, we study
Mo$_x$W$_{1-x}$Te$_2$ for $x = 0.07$ and 0.45 using pump-probe ARPES. The
system exhibits a dramatic response to the pump laser and we successfully
access states $> 0.2$eV above the Fermi level. For the first time, we observe
direct, experimental signatures of Fermi arcs in Mo$_x$W$_{1-x}$Te$_2$, which
agree well with theoretical calculations of the surface states. However, we
caution that the interpretation of these features depends sensitively on free
parameters in the surface state calculation. We comment on the prospect of
conclusively demonstrating a Weyl semimetal in Mo$_x$W$_{1-x}$Te$_2$.
