We report the discovery of 24 spectroscopic binary companions to giant stars. We fully constrain the orbital solution for 6 of these systems. We cannot unambiguously derive the orbital elements for the remaining stars because the phase coverage is incomplete. Of these stars, 6 present radial velocity trends that are compatible with long-period brown dwarf companions. The orbital solutions of the 24 binary systems indicate that these giant binary systems have a wide range in orbital periods, eccentricities, and companion masses. For the binaries with restricted orbital solutions, we find a range of orbital periods of between ∼ 97-1600 days and eccentricities of between ∼ 0.1-0.4. In addition, we studied the metallicity distribution of single and binary giant stars. We computed the metallicity of a total of 395 evolved stars, 59 of wich are in binary systems. We find a flat distribution for these binary stars and therefore conclude that stellar binary systems, and potentially brown dwarfs, have a different formation mechanism than planets. This result is confirmed by recent works showing that extrasolar planets orbiting giants are more frequent around metal-rich stars. Finally, we investigate the eccentricity as a function of the orbital period. We analyzed a total of 130 spectroscopic binaries, including those presented here and systems from the literature. We find that most of the binary stars with periods 30 days have circular orbits, while at longer orbital periods we observe a wide spread in their eccentricities. hand, the planetary formation follows the planet-metallicity correlation. This correlation tells us that planets form more efficiently around metal-rich stars (Gonzalez, 1997;Santos et al. 2001). When one of the stars in older stellar systems evolves off of the main sequence, the mutual effect of tidal interaction between them might dictate the final orbital configuration of the system. Verbunt & Phinney (1995) studied the orbital properties of binaries containing giant stars in open clusters. They showed that most of the binaries with periods shorter than ∼ 200 days present nearly circular orbits, which is most likely explained by the effect of the tidal circularization (Zahn 1977(Zahn , 1989Tassoul 1987Tassoul , 1988Tassoul , 1992. Similarly, Pan et al. (1998) showed that the predictions of Zahn's theories on synchronization for main-sequence binary systems are compatible with observational data. In addition, Massarotti et al. (2008, MAS08 hereafter) showed based on a sample 761 giant stars that all stars in binary systems with periods shorter than 20 days have circularized orbits. They also demonstrated that ∼50% of the orbits that have periods in the range of 20-100 days show significant eccentricity. This result shows the importance of studying the eccentricity distribution of binary Article number, page 1 of 17 A&A proofs: manuscript no. PBluhm