  Electronic Raman scattering and optical phonon self-energies are studied on
single crystals of $LuB_{12}$ with different isotopic composition in the
temperature region 10-650K and at pressures up to 10 GPa. The shape and energy
position of the spectral peaks depend on the magnitude of the probed wave
vector, temperature, and symmetry of excitations. We simulated experimental
spectra using electronic structure obtained in the density function theory and
taking into account the electron-phonon scattering. The emergence of a broad
continuum in the spectra is identified with the inelastic scattering of light
from the electronic intraband excitations. Their coupling to non-fully
symmetric phonon modes is the source of both the Fano interference and
temperature-dependent phonon self-energies. In addition, long wavelength
vibrations of the boron atoms are in nonadiabatic regime, so the electronic
contribution to their self-energies provides a temperature dependence that is
similar to the anharmonic contribution. Comparison of calculation and
experiment allowed us to determine the coupling constant $\lambda_{ep}$=0.32,
which gives correct critical temperature of the transition to the
superconducting state.
