We report the results of an experimental study of the magnetoresistance $rho_{xx}$ in two samples of $p$-Si/SiGe/Si with low carrier concentrations $p$=8.2$times10^{10}$ cm$^{-2}$ and $p$=2$times10^{11}$ cm$^{-2}$. The research was performed in the temperature range of 0.3-2 K in the magnetic fields of up to 18 T, parallel to the two-dimensional (2D) channel plane at two orientations of the in-plane magnetic field $B_{parallel}$ against the current $I$: $B_{parallel} perp I$ and $B_{parallel} parallel I$. In the sample with the lowest density in the magnetic field range of 0-7.2 T the temperature dependence of $rho_{xx}$ demonstrates the metallic characteristics ($d rho_{xx}/dT>$0). However, at $B_{parallel}$ =7.2 T the derivative $d rho_{xx}/dT$ reverses the sign. Moreover, the resistance depends on the current orientation with respect to the in-plane magnetic field. At $B_{parallel} cong$ 13 T there is a transition from the dependence $ln(Deltarho_{xx} / rho_{0})propto B_{parallel}^2$ to the dependence $ln(Deltarho_{xx} / rho_{0})propto B_{parallel}$. The observed effects can be explained by the influence of the in-plane magnetic field on the orbital motion of the charge carriers in the quasi-2D system.
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