2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/16538We have studied Shubnikov-de Haas oscillations in a two-dimensional electron system in silicon at low electron densities. Near the metal-insulator transition, only "spin" minima of the resistance at Landau-level filling factors 2, 6, 10, and 14 are seen, while the "cyclotron" minima at filling factors 4, 8, and 12 disappear. A simple explanation of the observed behavior requires a giant enhancement of the spin splitting near the metal-insulator transition.4 pages, postscript figures includedStrongly Correlated ElectronsMesoscale and Nanoscale Physicstext