The optical and transport properties in the paramagnetic phase of a-RuC1, are studied here for the first time. Values are reported for the dc conductivity of single crystals over the temperature range 110 to 500 OK in the two crystallographic directions, along and perpendicular to the optic c-axis: at 300 OK, ellc = 8 x 10' Rcm and e l c = 1.7 x 108 Rcm. The activation energy for both directions is = 0.1 eV below 300 OK and = 0.5 eV for temperatures above 400 OK. Detailed absorption spectra in the energy range 0.1 to 4 eV, and in the temperature interval 80 to 300 OK, reveal three weak bands (a = 10s om-l) a t = 0.28, 0.53, and 0.75 eV, two stronger peaks (a z lo4 to lo6 cm-l) at = 1.18, 2.08 and a step at 3.10 eV (values at 80°K). Reflectivity measurementsin the energy range 1 to 9 eV show maxima which, at 300OK, are centred at = 1.1, 1.9, and 3.10 eV and a marked reflection peak, at z 5.10 eV, probably related to p(c1) + s(Ru) band-to-band transitions. Ac photoconductivity spectra in the 0.6 to 2.8 eV region show structures closely related to the absorption bands in the same energy range. The different temperature dependence of the absorption and photocurrent spectra over the 80 to 300 O K interval is discussed. After an analysis of the transport data, the absorption spectrum up to 3 eV is discussed in terms of the Tanabe and Sugano diagram for a d6 configuration.Les propri6tes optiques et Blectriques de la phase paramagnetique du RuCl,-a ont 6t6 6tudi6es dans ce travail pour la premi&re fois. Nous avons report6 les valeurs de la conductivit6 Blectrique de cristaux de RuCl,-a entre 110 et 500 "K dans les deux directions cristal-

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