Single crystals of ${\mathrm{K}}_2$Pt${\mathrm{}\left(\mathrm{CN}\right)\mathrm{}}_4$${\mathrm{Br}}_{0.3}$·${\left({\mathrm{H}}_2\mathrm{O}\right)}_n$ show a Drude-type optical reflectivity for light polarized parallel to the crystal axis. The energy of the plasma edge indicates a metallic density of free carriers. The relatively small conductivity at dc and low frequencies and the photoconductivity at ${4.2}^{\mathrm{o}}$K can be understood in terms of a simple model assuming metallic strands interrupted by lattice defects.

• Received 27 August 1971

DOI:https://doi.org/10.1103/PhysRevLett.27.1060