Mixed order parameters, accidental nodes and broken time reversal   symmetry in organic superconductors: a group theoretical analysis
  We present a group theoretic analysis of several classes of organic superconductors. We argue that highly frustrated half-filled layered organic superconductors, such as kappa-(ET)_2Cu2(CN)_3 (where ET is BEDT-TTF) and beta'-[Pd(dmit)_2]_2X, undergo two superconducting phase transitions, the first from the normal state to a d-wave superconductor and the second to a d+id state. We show that the monoclinic distortion of kappa-(ET)_2Cu(NCS)_2 means that the symmetry of its superconducting order parameter is different from that of orthorhombic kappa-(ET)_2Cu[N(CN)_2]Br. We propose that quarter filled layered organic superconductors, e.g., theta-(ET)_2I_3, have d_{xy}+s order parameters. 
B. J. Powell