  Clathrate hydride \emph{Fm}\={3}\emph{m}-LaH$_{10}$ has been proven as the
most extraordinary superconductor with the critical temperature $T_c$ above 250
K upon compression of hundreds of GPa in recent years. A general hope is to
reduce the stabilization pressure and maintain the high $T_c$ value of the
specific phase in LaH$_{10}$. However, strong structural instability distorts
\emph{Fm}\={3}\emph{m} structure and leads to a rapid decrease of $T_c$ at low
pressures. Here, we investigate the phase stability and superconducting
behaviors of \emph{Fm}\={3}\emph{m}-LaH$_{10}$ with enhanced chemical
pre-compression through partly replacing La by Ce atoms from both experiments
and calculations. For explicitly characterizing the synthesized hydride, we
choose lanthanum-cerium alloy with stoichiometry composition of 1:1. X-ray
diffraction and Raman scattering measurements reveal the stabilization of
\emph{Fm}\={3}\emph{m}-La$_{0.5}$Ce$_{0.5}$H$_{10}$ in the pressure range of
140-160 GPa. Superconductivity with $T_c$ of 175$\pm$2 K at 155 GPa is
confirmed with the observation of the zero-resistivity state and supported by
the theoretical calculations. These findings provide applicability in the
future explorations for a large variety of hydrogen-rich hydrides.
