  We report the in-plane microwave surface impedance of a high quality single
crystal of \kappa-(BEDT-TTF)2Cu[N(CN)2]Br. In the superconducting state, we
find three independent signatures of d-wave pairing: i) a strong, linear
temperature dependence of superfluid density; ii) deep in the superconducting
state the quasiparticle scattering rate \Gamma ~ T^3; and iii) no BCS coherence
peak is observed in the quasiparticle conductivity. Above T_c, the
Kadowaki-Woods ratio and the temperature dependence of the in-plane
conductivity show that the normal state is a Fermi liquid below ~ 23 K, yet
resilient quasiparticles dominate the transport up to ~ 50 K.

Superconductivity;Strongly Correlated Electrons