Weak-localization-like temperature-dependent conductivity of a dilute two-dimensional hole gas in a parallel magnetic field

We have studied the magnetotransport properties of a high mobility two-dimensional hole gas (2DHG) in a 10 nm GaAs quantum well with densities in the range of (0.7-1.6)x10(10) cm (-2) on the metallic side of the zero-field ``metal-insulator transition.{''} In a parallel field well above B-c that suppresses the metallic conductivity, the 2DHG exhibits a conductivity Deltag(T)approximate to(1/pi) (e(2)/h)lnT reminiscent of weak localization for Fermi liquids. The experiments are consistent with the coexistence of two phases in our system: a metallic phase and a weakly insulating Fermi liquid phase.