Chemical evolution of inner Galactic disc at 4 kpc, computed with the same model parameters adopted in Spitoni et al. (2021), but using the stellar yields of Romano et al. (2010). Left panel: predicted age-metallicity relation highlighting the minimum [Fe/H] value after the bar formation (Age ≤ 8 Gyr). Right panel: evolution of abundance ratios [Fe/H] versus [X/Fe] (with X = Mg, Si, Ca). Large black-edged circles connected by a vertical green line indicate the predicted chemical composition of the ISM at the epoch of bar formation.