  We have studied electric-field-induced symmetry lowering in the tetragonal
(001)-oriented heteroepitaxial (Ba$_{0.8}$Sr$_{0.2}$)TiO$_3$ thin film
deposited on (001)MgO substrate. Polarized micro-Raman spectra were recorded
from the film area in between two planar electrodes deposited on the film
surface. Presence of \textit{c}-domains with polarization normal to the
substrate was confirmed from polarized Raman study under zero field, while
splitting and hardening of the \textit{E}(TO) soft mode and polarization
changes in the Raman spectra suggest monoclinic symmetry under external
electric field.
