Evolution of carrier density in the series ${\mathrm{YCu}}_{5\mathrm{-}\mathit{x}}$${\mathrm{In}}_{\mathit{x}}$

We present a study of the optical response of the series ${\mathrm{YCu}}_{5\mathrm{-}\mathit{x}}$${\mathrm{In}}_{\mathit{x}}$, with x varying from 0.97 to 1.1, in the spectral range 0.001–6 eV. The measured data show a large effect of the stoichiometry on the plasma frequency of these semimetallic compounds. The optical structures observed at energies above the plasma edge are investigated too. The results are discussed in terms of pressure effects, disorder, and electronic density of states. © 1996 The American Physical Society.