Possible high thermoelectric power factor in alkali-metal-intercalated BC${}_3$: anisotropic multiple valleys originating from the van Hove singularity of graphene

We theoretically investigate the electronic structure of monolayer BC${}_3$ and find that it hosts anisotropic multiple valleys originating from the splitting of the van Hove singularity in graphene. To make use of its favorable electronic structure, we investigate the electronic structure of alkali-metal-intercalated BC${}_3$, where intercalated atoms not only introduce electron carriers but also suppress interlayer coupling. We find that the interlayer transfer is effectively suppressed by potassium intercalation, by which the favorable electronic structure of monolayer BC${}_3$ is preserved. Finally, we perform model calculation with the onsite-energy offset, and we verify that the strategy of introducing the splitting to the van Hove singularity works well.