  Dirac semi-metals show a linear electronic dispersion in three dimension
described by two copies of the Weyl equation, a theoretical description of
massless relativistic fermions. At the surface of a crystal, the breakdown of
fermion chirality is expected to produce topological surface states without any
counterparts in high-energy physics nor conventional condensed matter systems,
the so-called "Fermi Arcs". Here we present Shubnikov-de Haas oscillations
involving the Fermi Arc states in Focused Ion Beam prepared microstructures of
Cd$_3$As$_2$. Their unusual magnetic field periodicity and dependence on sample
thickness can be well explained by recent theoretical work predicting novel
quantum paths weaving the Fermi Arcs together with chiral bulk states, forming
"Weyl orbits". In contrast to conventional cyclotron orbits, these are governed
by the chiral bulk dynamics rather than the common momentum transfer due to the
Lorentz force. Our observations provide evidence for direct access to the
topological properties of charge in a transport experiment, a first step
towards their potential application.
