  In periodic media, despite the close relationship between geometrical effects
in the bulk and topological surface states, the two are typically probed
separately. We show that when beams in a Weyl medium reflect off an interface
with a gapped medium, the trajectory is influenced by both bulk geometrical
effects and the Fermi arc surface states. The reflected beam experiences a
displacement, analogous to the Goos-H\"anchen or Imbert-Fedorov shifts, that
forms a half-vortex in the two-dimensional surface momentum space. The
half-vortex is centered where the Fermi arc of the reflecting surface touches
the Weyl cone, with the magnitude of the shift scaling as an inverse square
root away from the touching-point, and diverging at the touching-point. This
striking feature provides a way to use bulk transport to probe the topological
characteristics of a Weyl medium.
