Resistivity Anisotropy in Non-Superconducting Ba sub (2.2) Sr sub (1.8) CuO sub 6

We have measured the resistivity anisotropy in single crystals of nominal comosition Ba sub (2.2) Sr sub (1.8) CuO sub 6, the single-copper-layer analog of the 85K superconductor Ba sub 2 Sr sub 2 CaCu sub 2 O sub 8. We find that the crystals are un-twinned with a strong superlattice of 5b sub o X 2c sub o. The resistivity anisotropy was measured by the Montgomery Methods in the range 4 - 500K, and ac inductance techniques were used to probe for superconductivity down to 1.5K. The in-plane resistivity is metallic at high temperatures and becomes non-metallic below 20K. The low-temperature in-plane resistance is suggestive of two-dimensional localization. The out-of-plane component of the resistivity, p sub c is non-metallic over the entire temperature range. The increase of p sub c at low temperatures is weaker than the 1/T dependence seen in Ba sub 2 Sr sub 2 CaCu sub 2 O sub 8. The resistance ratio p sub c /p sub (ab) is on the order of 10 sup 5, a number comparable to that measured in Ba sub 2 Sr sub 2 CaCu sub 2 O sub 8. No indication of superconductivity was seen above 1.5 K.