Chemical characterisation of the thick disc and YAR sample for red giant-type stars. Top panels: MDFs and [α/Fe] distribution functions of the YAR (in solid black lines) and thick disc (in dashed grey lines) samples. f = N_i/N_tot represents the fractional number density where N_i is the number of stars in each bin of [Fe/H] or [α/Fe] and N_tot is the total number of stars of the sample. Bottom panels: [α/Fe]−[Fe/H] distribution for YAR stars (black dots, left panel) and a randomly selected thick disc subsample (empty dots, right panel), both containing the same number of stars (written the relative legends.) The potential YAR binaries are denoted by squares: yellow squares indicate stars that exhibit at least one indicator of being a binary, while the magenta square represents the single star that fulfils all the examined indicators (see Sect. 2.2). In both plots, the coloured lines represent stellar density iso-contours of the entire thick disc sample: 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%, and 5% of the peak density.