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## Electron-electron interaction correction and magnetoresistance in tilted fields in Si-based two-dimensional systems

We study the diffusive electron-electron interaction correction to conductivity by analyzing simultaneously ρxx and ρxy for disordered 2D electron systems in Si in a tilted magnetic field. Tilting the field is shown to be a straightforward tool to disentangle spin and orbital effects. In particular, by changing the tilt angle we prove experimentally that in the field range gμBB>kBT the correction depends on the modulus of the magnetic field rather than on its direction, which is expected for a system with isotropic g factor. In the high-field limit, the correction behaves as ln(B), as expected theoretically [Lee and Ramakrishnan, Phys. Rev. B 26, 4009 (1982)]. Our data prove that the diffusive electron-electron interaction correction to conductivity is not solely responsible for the huge and temperature-dependent magnetoresistance in a parallel field, typically observed in Si-MOSFETs.