Composite fermions and quartets in the Fermi-Bose mixture with   attractive interaction between fermions and bosons
  We consider a model of Fermi-Bose mixture with strong hard-core repulsion between particles of the same sort and attraction between particles of different sorts. In this case, besides the standard anomalous averages of the type $<b>$; $<bb>$ and $<cc>$, a pairing between fermion and boson of the type $bc$ is possible. This pairing corresponds to a creation of composite fermions in the system. At low temperatures and equal densities of fermions and bosons composite fermions are further paired in quartets. Our investigations are important for high-$T_c$ superconductors and in connection with recent observation of weakly bound dimers in magnetic traps at ultralow temperatures. 
M.Yu. Kagan, I.V. Brodsky (1), D.V. Efremov (2), A.V. Klaptsov (3)   ((1) P.L. Kapitza Institute for Physical Problems, (2) ...