  It is demonstrated that in a two--band 2D system the resonance state is
manifested close to the energy of the Dirac point in the electron spectrum for
the sufficiently large impurity perturbation. With increasing the impurity
concentration, the electron spectrum undergoes the rearrangement, which is
characterized by the opening of the broad quasi--gap in the vicinity of the
nodal point. If the critical concentration for the spectrum rearrangement is
not reached, the domain of localized states remains exponentially small
compared to the bandwidth.
