TERMINATION OF THE INTEGER QHE BY AN ELECTRON-SOLID IN A DILUTE 2D-ELECTRON SYSTEM AT MK-TEMPERATURES

Upon decreasing the density, the 2D electron system exhibits a transit ion from the metallic state, characterized by the Quantum Hall effect, to the collective insulating state (electron solid), interrupted by t he Quantum Hall effect at integer filling factor nu = 1, 2, and 6. The electron solid shows many features attributed to the pinned Wigner cr ystal. On the basis of the longitudinal and Hall resistance measuremen ts through these reentrant transitions, we discuss the pathway for the disappearance of delocalized states.