Angular dependence of the c-axis normal state magnetoresistance in single crystal Tl2Ba2CuO6

We report measurements of the normal state magnetoresistance (MR) from 30 to 340 K in fields B up to 13 T for single crystals of overdoped Tl2Ba2CuO6 (T-c less than or equal to 25 K). For out-of-plane current flow, the transverse MR Delta rho(c)/rho(c) is large and positive. On rotating B within the a-b plane, Delta rho(c)/rho(c) exhibits a striking anisotropy with fourfold symmetry. The amplitude of this effect increases as B-4 and the maximum MR occurs for B along the [110] crystallographic directions, i.e., at 45 degrees to the Cu-O-Cu bonds. This the first direct evidence for anisotropy of the in-plane mean free path in the cuprates.