  The far-infrared in-plane reflectivity of the organic superconductor
$\alpha_t$-(BEDT-TTF)$_{2}$I$_{3}$ is measured down to frequencies of 10
cm$^{-1}$; the optical conductivity is obtained by a Kramers-Kronig procedure.
In the superconducting state an energy gap opens at 25 cm$^{-1}$ which
corresponds to $2\Delta/k_BT_c = 4.4$ in agreement with moderate coupling. Even
well below $T_c=8$ K a considerable absorption remains for
$\hbar\omega<2\Delta$. We discuss different posibilities to explain this
behaviour.
