  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
$\ln(\Delta\rho_{xx} / \rho_{0})\propto B_{\parallel}^2$ to the dependence
$\ln(\Delta\rho_{xx} / \rho_{0})\propto B_{\parallel}$. 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.
