Top panel: Relation between [Al/Fe] and [Fe/H] for the stellar sample. The elemental abundances derived under NLTE assumptions for the Al I 3961 Å line. The data are colour-coded by high-Al and low-Al, with symbols following the classification of (Nissen & Schuster 2010). Thick-disc stars are represented by crosses, high-α stars are shown as diamonds, and low-α stars as circles. Bottom panel: Distribution of the stellar sample in the [Mg/Fe]_NLTE versus [Fe/H]_LTE, according to the low-Al and high-Al classification used in this paper, adopting the same symbols as the top panel.