  It is shown that in crystal lattices with a basis the cooperative behavior of
a certain type of atoms performing optical long-wavelength vibrations in a
double-well potential of the field of the matrix lattice may lead to the
formation of a bistable sublattice. As a result of the interaction of the
metastable states of such a sublattice with the vibrational states of the
matrix lattice, the elastic and thermal properties of the crystal acquire
anomalous, hysteresis-like, temperature curves. The concepts developed in the
paper make it possible to obtain a qualitative interpretation, which agrees
with the experimental data, of the hysteresis-like temperature dependence of
the speed and absorption of ultrasonic waves, the specific heat, and the
thermal conductivity in superconducting yttrium and bismuth cuprates.
