  We present the discovery of a white dwarf companion at 3.6" from GJ3346, a
nearby ($\pi\sim$42 mas) K star observed with SPHERE@VLT as part of an open
time survey for faint companions to objects with significant proper motion
discrepancies ($\Delta\mu$) between Gaia DR1 and Tycho-2. Syrius-like systems
like GJ3346AB, which include a main sequence star and a white dwarf, can be
difficult to detect because of the intrinsic faintness of the latter. They
have, however, been found to be common contaminants for direct imaging
searches. White dwarfs have in fact similar brightness to sub-stellar
companions in the infrared, while being much brighter in the visible bands like
those used by Gaia. Combining our observations with Gaia DR2 and with several
additional archival data sets, we were able to fully constrain the physical
properties of GJ3346B, such as its effective temperature
(11$\times$10$^3\pm$500 K) as well as the cooling age of the system (648$\pm$58
Myrs). This allowed us to better understand the system history and to partially
explains the discrepancies previously noted in the age indicators for this
objects. Although further investigation is still needed, it seems that GJ3346,
which was previously classified as young, is in fact most likely to be older
than 4 Gyrs. Finally, given that the mass (0.58$\pm$0.01$M_{\odot}$)} and
separation (85 au) of GJ3346B are compatible with the observed $\Delta\mu$,
this discovery represents a further confirmation of the potential of this kind
of dynamical signatures as selection methods for direct imaging surveys
targeting faint, sub-stellar companions.
