  The Nambu-Gorkov Green's function approach is applied to strongly type-II
superconductivity in a 2D spin-momentum locked (Weyl) Fermi gas model at high
perpendicular magnetic fields. When the chemical potential is sufficiently
close to the branching (Dirac) point, such that the cyclotron effective mass,
$m^{\ast }$, is a very small fraction of the free electron mass, $m_{e}$,
relatively large portion of the $H-T$ phase diagram is exposed to
magneto-quantum oscillation effects. This model system is realized in the 2D
superconducting state, observed recently on the surface of the topological
insulator Sb$_{2}$Te$_{3} $, for which high field measurements were reported at
low carrier densities with $m^{\ast}=0.065m_{e}$. Calculations of the pairing
condensation energy in such a system, as a function of $H$ and $T$, using both
the Weyl model and a reference standard model, that exploits a simple quadratic
dispersion law, are found to yield indistinguishable results in comparison with
the experimental data. Significant deviations from the predictions of the
standard model are found only for very small carrier densities, when the
cyclotron energy becomes very large, the Landau level filling factors are
smaller than unity, and the Fermi energy shrinks below the cutoff energy.
