  The synthesis of transition metals in a two-dimensional (2D) fashion has
attracted growing attention for both fundamental and application-oriented
investigations, such as 2D magnetism, nanoplasmonics and non-linear optics.
However, the large-area synthesis of this class of materials in a single-layer
form poses non-trivial difficulties. Here we present the synthesis of a
large-area 2D gold layer, stabilized in between silicon carbide and monolayer
(ML) graphene. We show that the 2D-Au ML is a semiconductor with the valence
band maximum 50 meV below the Fermi level. The graphene and gold layers are
largely non-interacting, thereby defining a novel class of van der Waals
heterostructure. The 2D-Au bands, exhibit a 225 meV spin-orbit splitting along
the {\Gamma K} direction, making it appealing for spin-related applications. By
tuning the amount of gold at the SiC/graphene interface, we induce a
semiconductor to metal transition in the 2D-Au, which was never observed before
and hosts great interest for fundamental physics.
