  We report an infrared ellipsometry study of the charge carrier dynamics in
polycrystalline Kxp-terphenyl samples with nominal $x=3$, for which signatures
of high-temperature superconductivity were previously reported. The infrared
spectra are dominated by two Lorentzian bands with maxima around 4 000
cm$^{-1}$ and 12 000 cm$^{-1}$ which, from a comparison with calculations based
on a H\"uckel model are assigned to intra-molecular excitations of $\pi$
electrons of the anionic p-terphenyl molecules. The inter-molecular electronic
excitations are much weaker and give rise to a Drude peak and a similarly weak
Lorentzian band around 220 cm$^{-1}$. A dc resistivity of about 0.3 $\Omega$ cm
at 300 K is deduced from the IR data, comparable to values measured by
electrical resistivity on a twin sample. The analysis of the temperature
dependence of the low-frequency response reveals a gradual decrease of the
plasma frequency and the scattering rate of the Drude peak below 300 K that
gets anomalously enhanced below 90 K. The corresponding missing spectral weight
of the Drude peak appears blue-shifted towards the Lorentz-band at 220
cm$^{-1}$. This characteristic blue-shift signifies an enhanced localization of
the charge carriers at low temperatures and contrasts the behavior expected for
a bulk superconducting state for which the missing spectral weight would be
redshifted to a delta-function at zero frequency that accounts for the
loss-free response of the superconducting condensate. Our data might still be
compatible with a filamentary superconducting state with a volume fraction well
below the percolation limit for which the spatial confinement of the condensate
can result in a plasmonic resonance at finite frequency.
