Shubnikov–de Haas oscillations have been studied, at low temperatures, in a high-mobility quantum-Hall-effect sample. A linear increase with increasing magnetic field of the peak values of resistance is observed and is explained quantitatively by a quantum diffusion model with predominantly small-angle scattering. The results are inconsistent with recent suggestions that the peak values of conductivity, between integer-quantum-Hall-effect plateaus, are ${\mathit{e}}^2$/2h.

• Received 2 February 1994

DOI:https://doi.org/10.1103/PhysRevB.49.10798