  We study the possibility of excitonic pairing in layered degenerate
semimetals such as graphite, where the electron density of states almost
vanishes at the Fermi level and, therefore, the Coulomb interactions remain
essentially unscreened. By focusing on the Dirac-like low-energy electron
excitations and numerically solving a non-linear gap equation for the order
parameter, we obtain a critical value of the Coulomb coupling and establish the
Kosterlitz-Thouless-like nature of a putative semimetal-to-excitonic insulator
transition.
