Resistance Ridges Along Filling Factor V=4i In Sio2/Si/Sio2 Quantum Wells

We examine Landau level coincidences in SiO2/Si(100)/SiO2 quantum wells. Surprisingly, under certain conditions of apparent multiple degeneracy, our data reveal strikingly novel behavior where the resistance is elevated at filling factors that are integer multiples of 4. This structure persists when underlying single particle energies are swept leading to resistance ridges running along v = 4i. The data suggest a new type of many-body effect due to the combined degeneracy of valley and spin.