  Irreducible second-order Darboux transformations are applied to the periodic
Schrodinger's operators. It is shown that for the pairs of factorization
energies inside of the same forbidden band they can create new non-singular
potentials with periodicity defects and bound states embedded into the spectral
gaps. The method is applied to the Lame and periodic piece-wise transparent
potentials. An interesting phenomenon of translational Darboux invariance
reveals nonlocal aspects of the supersymmetric deformations.
