We examine the effect of an in-plane magnetic field on the resistance of a 2-dimensional electron system confined in a silicon quantum well when the Fermi energy is tuned through the upper valley-subband edge while the electrons are otherwise valley-polarized. In contrast to previous experiments on valley-degenerate systems which only showed positive magnetoresistance, when the Fermi energy is at or near the upper valley-subband edge, the magnetoresistance is found to show a distinct negative contribution which is interpreted as being due to spin polarization of the upper valley-subband.
Takashina, K., Niida, Y., Renard, V. T., Fujiwara, A., Fujisawa, T., & Hirayama, Y. (2009). Negative magnetoresistance of a silicon 2deg under in-plane magnetic field due to spin-splitting of upper subbands. International Journal of Modern Physics B, 23(12 & 13), 2938-2942. https://doi.org/10.1142/S021797920906258X