Structural and electronic properties of T graphene: a two-dimensional carbon allotrope with tetrarings.

T graphene, a two-dimensional carbon allotrope with tetrarings, is investigated by first-principles calculations. We demonstrate that buckled T graphene has Dirac-like fermions and a high Fermi velocity similar to graphene even though it has nonequivalent bonds and possesses no hexagonal honeycomb structure. New features of the linear dispersions that are different from graphene are revealed. π and π* bands and the two comprising sublattices are the key factors for the emergence of Dirac-like fermions. T graphene and its two types of nanoribbon are expected to possess additional properties over graphene due to its different band structure.