  We studied the nearby edge-on galaxy NGC4656 and its dwarf low surface
brightness companion with the enhanced UV brightness, NGC4656UV, belonging to
the interacting system NGC4631/56. Regular photometric structure and relatively
big size of NGC4656UV allows to consider this dwarf galaxy as a separate group
member rather than a tidal dwarf. Spectral long-slit observations were used to
obtain the kinematical parameters and gas-phase metallicity of NGC4656UV and
NGC4656. Our rough estimate of the total dynamical mass of NGC4656UV allowed us
to conclude that this galaxy is the dark-matter dominated LSB dwarf or ultra
diffuse galaxy. Young stellar population of NGC4656UV, as well as strong local
non-circular gas motions in NGC4656 and the low oxygen gas abundance in the
region of this galaxy adjacent to its dwarf companion, give evidence in favour
of the accretion of metal-poor gas onto the discs of both galaxies.
