Sn atomic layers attract considerable interest owing to their spin-related physical properties caused by their strong spin-orbit interactions. We performed Sn intercalation into the graphene/SiC(0001) interface and found a new type of Sn atomic layer. Sn atoms occupy on-top sites of Si-terminated SiC(0001) with in-plane Sn-Sn bondings, resulting in a triangular lattice. Angle-resolved photoemission spectroscopy revealed characteristic dispersions at and points, which agreed well with density functional theory calculations. The Sn triangular lattice atomic layer at the interface showed no oxidation upon exposure to air, which is useful for characterization and device fabrication ex situ.
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