[C/Fe] ratios in the populations of stars with and without planets. Upper panel: [C/Fe] as a function of metallicity for stars with and without detected planets. Low-mass planets are depicted with blue triangles meanwhile stars with high-mass planets are shown with red squares. Black dots represent single stars. The two Jupiter-like hosts with a green circle around are HD 171028 and HD 190984. Bottom panel: same as above but the mean abundances for each group of stars are shown in each metallicity bin of 0.1 dex together with the standard error of the mean.