  It is shown that the Dirac fermion structures created in the middle of the
Landau bands in the vortex-lattice state of a pure 2D strongly type-II
superconductor at half-integer filling factors can be effectively controlled by
the external magnetic field. The resulting field-induced modulation of the
magneto-oscillations is shown to arise from Fermi-surface resonance scattering
in the vortex core regions. Possible observation of the predicted effect in a
quasi 2D organic superconductor is discussed.
