  The unusual electronic properties of single-layer graphene make it a
promising material system for fundamental advances in physics, and an
attractive platform for new device technologies. Graphene's spin transport
properties are expected to be particularly interesting, with predictions for
extremely long coherence times and intrinsic spin-polarized states at zero
field. In order to test such predictions, it is necessary to measure the spin
polarization of electrical currents in graphene. Here, we resolve spin
transport directly from conductance features that are caused by quantum
interference. These features split visibly in an in-plane magnetic field,
similar to Zeeman splitting in atomic and quantum dot systems. The
spin-polarized conductance features that are the subject of this work may, in
the future, lead to the development of graphene devices incorporating
interference-based spin filters.
