Period-eccentricity diagram for the binary systems in our sample. Red and blue symbols denote CEMP-s and CEMP-r/s stars, respectively. Systems with periods P< 3000 days are plotted as right-pointing triangles to indicate that the orbital parameters are still uncertain; their periods, in particular, may well be even longer. Black dots and crosses: Comparison sample of 141 giant binary members of Galactic open clusters of all ages (Mermilliod et al. 2007; Mathieu et al. 1990) and 16 metal-poor and C-normal binaries from Carney et al. (2003).