  We intercalate a van der Waals heterostructure of graphene and hexagonal
Boron Nitride with Au, by encapsulation, and show that Au at the interface is
two dimensional. A charge transfer upon current annealing indicates
redistribution of Au and induces splitting of the graphene bandstructure. The
effect of in plane magnetic field confirms that splitting is due to
spin-splitting and that spin polarization is in the plane, characteristic of a
Rashba interaction with magnitude approximately 25 meV. Consistent with the
presence of intrinsic interfacial electric field we show that the splitting can
be enhanced by an applied displacement field in dual gated samples. Giant
negative magnetoresistance, up to 75%, and a field induced anomalous Hall
effect at magnetic fields < 1 T are observed. These demonstrate that hybridized
Au has a magnetic moment and suggests the proximity to formation of a
collective magnetic phase. These effects persist close to room temperature.
