Weak antilocalization in a 2D electron gas with the chiral splitting of the spectrum

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.