  We explore condensation temperature Tc trends in the unique binary system
Zet1 Ret - Zet2 Ret, to determine whether there is a depletion of refractories,
which could be related to the planet formation process. The star Zet2 Ret hosts
a debris disk which was detected by an IR excess and confirmed by direct
imaging and numerical simulations, while Zet1 Ret does not present IR excess
nor planets. We carried out a high-precision abundance determination in both
components of the binary system via a line-by-line, strictly differential
approach. The stellar parameters Teff , log g, [Fe/H] and vturb were determined
by imposing differential ionization and excitation equilibrium of Fe I and Fe
II lines, with an updated version of the program FUNDPAR. The star Zet1 Ret
resulted slightly more metal rich than Zet2 Ret by 0.02 dex. In the
differential calculation of Zet1 Ret using Zet2 Ret as reference, the
abundances of the refractory elements resulted higher than the volatile
elements, and the trend of the refractory elements with Tc showed a positive
slope. These facts together show a lack of refractory elements in Zet2 Ret (a
debris-disk host) relative to Zet1 Ret. The Tc trend would be in agreement with
the proposed signature of planet formation (Melendez et al. 2009) rather than
possible Galactic Chemical Evolution or age effects, which are largely
diminished here. Then, following the interpretation of Melendez et al. (2009),
we propose an scenario in which the refractory elements depleted in Zet2 Ret
are possibly locked-up in the rocky material that orbits this star and produce
the debris disk observed around this object. We estimated a lower limit of
Mrock = 3 Me for the rocky mass of depleted material, which is compatible with
a rough estimation of 3-50 Me of a debris disk mass around a solar-type star
(Krivov et al. 2008). (abridged)
