Probing the order parameter of the layered organic superconductor kappa-(BEDT-TTF)(2) Cu[N(CN)(2)]Br by ac susceptibility measurements

ac susceptibility measurements are reported for single crystals of the laye red organic superconductor kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Br. The value of the out-of-plane penetration depth lambda(b)(0) was found to be 133 mu m, c onsistent with earlier results. The temperature dependence of the in-plane superfluid density, with the value of in-plane component lambda(ac)(O) of t he order of 1 mu m, is strongly linear in T, whereas the out-of-plane super fluid density varies as T-2 at low temperatures. The observed behavior is f ully consistent with the one expected for d-wave superconductivity.