  The low-lying states of graphene contain exciting topological properties that
depend on the interplay of different symmetry breaking terms. The corresponding
energy gaps remained unexplored until recently, owing to the low energy scale
of the terms involved (few tens of ueV). These low energy terms include
sublattice splitting, the Rashba and the intrinsic spin-orbit coupling, whose
balance determines the topological properties. In this work, we unravel the
contributions arising from the sublattice and the intrinsic spin orbit
splitting in graphene on hexagonal boron-nitride. Employing
resistively-detected electron spin resonance, we measure a sublattice splitting
of the order of 20E-6 eV, and confirm an intrinsic spin orbit coupling of
approximately 45E-6 eV. The dominance of the latter suggests a topologically
non-trivial state, involving fascinating properties. Electron spin resonance is
a promising route towards unveiling the intriguing band structure at low energy
scales.
