  We study analytically the structural properties of a system with a
short-range attraction and a competing long-range screened repulsion. This
model contains the essential features of the effective interaction potential
among charged colloids in polymeric solutions and provides novel insights on
the equilibrium phase diagram of these systems. Within the self-consistent
Hartree approximation and by using a replica approach, we show that varying the
parameters of the repulsive potential and the temperature yields a phase
coexistence, a lamellar and a glassy phase. Our results strongly suggest that
the cluster phase observed in charged colloids might be the signature of an
underlying equilibrium lamellar phase, hidden on experimental time scales.
