  We present an extension and revision of the spectroscopic and structural data
of the mixed stack charge transfer (CT) crystal
3,3$^\prime$,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 revise
the 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, and
is consistent with the vibrational data. However, polarized Raman data in the
low-frequency region also indicate that by increasing temperature above 200 K
the structure presents an increasing degree of disorder mainly along the stack
axis. X-ray diffraction data at room temperature have confirmed that the
correct structure is $P2_1/m$ -- no phase transitions -- but did not allow to
definitely substantiate the presence of disorder. On the other hand, dielectric
measurement have evidenced a typical relaxor ferroelectric behavior already at
room temperature, with a peak in real part of dielectric constant
$\epsilon'(T,\nu)$ around 200 K and 0.1 Hz. The relaxor behavior is explained
in terms of the presence of spin solitons separating domains of opposite
polarity that yield to ferroelectric nanodomains. TMB-TCNQF4 is confirmed to be
a narrow gap band semiconductor ($E_a \sim 0.3$ eV) with room temperature
conductivity of $\sim 10^{-4}~ \Omega^{-1}$ cm$^{-1}$.
