The optical conductivities of single crystals of LuAl2 and YbAl2 were measu
red by spectroscopic ellipsometry in the energy range of 1.4-5.5 eV for LuA
l2 and 1.4-5.2 eV for YbAl2. The optical conductivity spectra of LuAl2 and
YbAl2 show similar features except for a difference in magnitude. Both have
peaks near 1.8-2.1 eV and broad shoulders between 3.0 and 4.0 eV. The shou
lder is weaker in YbAl2. The band structure, density of states, and optical
conductivity were calculated with the tight-binding linear muffin-tin orbi
tal method in the atomic sphere approximation. The calculated optical condu
ctivity with the inclusion of energy-dependent broadening agrees well with
the experimental data. Oxidation effects on the surface of the sample were
modeled using a three-phase model. The calculated optical conductivity of t
he clean surface is enhanced over that of the oxidized surface.