pi-shifted magnetoconductance oscillations in mesoscopic superconducting-normal heterostructures

Interference of proximity-induced superconducting correlations in mesoscopi c metallic rings is sensitive to the magnetic flux Phi inside these rings. This is the reason for magnetoconductance oscillations in such systems. We detected experimentally and explained theoretically a novel effect: the pha se of these oscillations can switch between 0 and pi depending on the resis tance of intermetallic interfaces and temperature. The effect is due to a n ontrivial interplay between the proximity-induced enhancement of the local conductivity and the proximity-induced suppression of the density of states at low energies.