  The long theorized two-dimensional allotrope of SiC has remained elusive amid
the exploration of graphenelike honeycomb structured monolayers. It is
anticipated to possess a large direct band gap (2.5 eV), ambient stability, and
chemical versatility. While $sp^{2}$ bonding between silicon and carbon is
energetically favorable, only disordered nanoflakes have been reported to date.
Here we demonstrate large-area, bottom-up synthesis of monocrystalline,
epitaxial monolayer honeycomb SiC atop ultrathin transition metal carbide films
on SiC substrates. We find the 2D phase of SiC to be almost planar and stable
at high temperatures, up to 1200{\deg}C in vacuum. Interactions between the
2D-SiC and the transition metal carbide surface result in a Dirac-like feature
in the electronic band structure, which in the case of a TaC substrate is
strongly spin-split. Our findings represent the first step towards routine and
tailored synthesis of 2D-SiC monolayers, and this novel heteroepitaxial system
may find diverse applications ranging from photovoltaics to topological
superconductivity.

Materials Science