FIELD AND FREQUENCY-DEPENDENT TRANSPORT IN THE 2-DIMENSIONAL ORGANIC CONDUCTOR ALPHA-(BEDT-TTF)2I3

The title compound undergoes a metal-insulator phase transition of unk nown origin at T(MI) = 135 K. We studied the electrodynamic response o f alpha-(BEDT-TTF)2I3 in a wide range of frequency, covering microwave and millimeter wave frequencies as well as the optical spectral range , and found a frequency dependent conductivity up to 1000 cm-1 in the low temperature phase. This is accompanied be a non-linear transport w ith a smooth onset at about 10 V/cm. Our X-ray studies show no indicat ion of superstructure reflections and clearly rule out the formation o f a charge density wave ground state. The lack of a temperature depend ence in the millimeter wave conductivity between 20 K and 100 K makes hopping transport unlikely.