Ferroelectric properties of charge-ordered alpha-(BEDT-TTF)2I3
  A detailed investigation of the out-of-plane electrical properties of charge-ordered alpha-(BEDT-TTF)2I3 provides clear evidence for ferroelectricity. Similar to multiferroic alpha-(BEDT-TTF)2Cu[N(CN)2]Cl, the polar order in this material is ascribed to the occurrence of bond- and site-centered charge order. Dielectric response typical for relaxor ferroelectricity is found deep in the charge-ordered state. We suggest an explanation in terms of the existence of polar and nonpolar stacks of the organic molecules in this material, preventing long-range ferroelectricity. The results are discussed in relation to the formation or absence of electronic polar order in related charge-transfer salts. 
P. Lunkenheimer, B. Hartmann, M. Lang, J. M\"uller, D. Schweitzer, S.   Krohns, and A. Loidl
cond-mat.str-el cond-mat.mtrl-sci