(a) Schematic illustration of time-reversed scattering loops in the quantum diffusion regime in disordered metals. The open circles represent impurities and the arrows mark the trajectories that electrons travel. (b) and (c) The signatures of the weak antilocalization (WAL) in (b) temperature (T) dependence of the conductivity σ and (c) magnetoconductivity [defined as δσ ≡ σ(B) − σ(0)], where B is the magnetic field.