  Spin orbit interaction (SOI) having a complicated energy spectrum with a
conical point and four critical points are promising candidates to observe
electron topological transitions. In the present paper we have investigated the
evolution of the electron spectrum and isoenergetic contours under the
influence of parallel magnetic field. General formulas for energies of critical
points for arbitrary values of SOI constants and magnetic field are found. The
existence of critical magnetic fields at which a number of critical points is
changed has been predicted. The magnetic field driving topological Lifshitz
transitions in the geometry of isoenergetic contours have been studied. Van
Hove's singularities in the electron density of states are calculated. The
obtained results can be used for theoretical investigations of different
electron characteristics of such 2D systems.
