  The family of molecular conductors TMTTF/TMTSF-X demonstrates almost all
known electronic phases in parallel with a set of weak structural modifications
of anion ordering and mysterious structureless transitions. Only in early
2000's their nature became elucidated by discoveries of a huge anomaly in the
dielectric permittivity and by the NMR evidences for the charge ordering
(disproportionation). These observations have been interpreted as the never
expected ferroelectric transition. The phenomenon unifies a variety of
different concepts and observations in quite unusual aspects or conjunctions:
ferroelectricity of good conductors, structural instability towards the
Mott-Hubbard state, Wigner crystallization in a dense electronic system, the
ordered 4K_F density wave, richness of physics of solitons, interplay of
structural and electronic symmetries. The corresponding theory of the "combined
Mott-Hubbard state" deals with orthogonal contributions to the Umklapp
scattering of electrons coming from the two symmetry breaking effects: the
build-in nonequivalence of bonds and the spontaneous nonequivalence of sites.
The state gives rise to several types of solitons, all of them showing in
experiments. On this basis we can interpret the complex of existing
experiments, and suggest some future ones, such as optical absorption and
photoconductivity, combined ferroelectric resonance and the phonon
anti-resonance, plasma frequency reduction.
