  Motivated by the recent observation of the metal-insulator transition in
Si-MOSFETs we consider the quantum interference correction to the conductivity
in the presence of the Rashba spin splitting. For a small splitting, a
crossover from the localizing to antilocalizing regime is obtained. The
symplectic correction is revealed in the limit of a large separation between
the chiral branches. The relevance of the chiral splitting for the 2D electron
gas in Si-MOSFETs is discussed.
