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We present an extension and revision of the spectroscopic and structural dataof the mixed stack charge transfer (CT) crystal3,3$^\prime$,5,5$^\prime$-tetramethylbenzidine--tetrafluoro-tetracyanoquinodimethane(TMB-TCNQF4), associated with new electric and dielectric measurements.Refinement of syncrotron structural data at low temperature has led to revisethe previously reported [Phys. Rev. Mat. 2, 024602 (2018)] $C2/m$ structure.The revised structure is $P2_1/m$, with two dimerized stacks per unit cell, andis consistent with the vibrational data. However, polarized Raman data in thelow-frequency region also indicate that by increasing temperature above 200 Kthe structure presents an increasing degree of disorder mainly along the stackaxis. X-ray diffraction data at room temperature have confirmed that thecorrect structure is $P2_1/m$ -- no phase transitions -- but did not allow todefinitely substantiate the presence of disorder. On the other hand, dielectricmeasurement have evidenced a typical relaxor ferroelectric behavior already atroom temperature, with a peak in real part of dielectric constant$\epsilon'(T,\nu)$ around 200 K and 0.1 Hz. The relaxor behavior is explainedin terms of the presence of spin solitons separating domains of oppositepolarity that yield to ferroelectric nanodomains. TMB-TCNQF4 is confirmed to bea narrow gap band semiconductor ($E_a \sim 0.3$ eV) with room temperatureconductivity of $\sim 10^{-4}~ \Omega^{-1}$ cm$^{-1}$.

Tetramethylbenzidine-TetrafluoroTCNQ: A narrow-gap semiconducting salt with room temperature relaxor ferroelectric behavior