  The discovery of topological phases introduces new perspectives and platforms
for various interesting physics originally investigated in quantum context and
then, on an equal footing, in classic wave systems, such as photonics,
acoustics and mechanics. As a characteristic feature, nontrivial Fermi arcs,
connecting between topologically distinct Fermi surfaces, play vital roles in
the clarification of Dirac and Weyl semimetals and have been observed in
quantum materials very recently. However, in classical systems, no direct
experimental observation of Fermi arcs in the momentum space has been reported
so far. Here, using near-field scanning measurements, we show the observation
of a photonic Fermi arcs connecting topologically distinct bulk states in
chiral hyperbolic metamaterials. To verify the topological nature of this
system, we further observe backscattering-immune propagation of nontrivial
surface wave across a three-dimension physical step. Our results demonstrate
metamaterial approach towards topological photonics and offer a deeper
understanding of topological phases in three-dimension classical systems.
