Distribution of the AMBRE synthetic spectra grid in the atmospheric parameters and [α/Fe] space. We reiterate that only one value of [α/Fe] for every [M/H] was adopted during the model atmosphere selection process. This is illustrated in the bottom right panel where the AMBRE spectra computed from MARCS models with consistent [α/Fe] ratios are plotted with filled circles while open circles refer to all the other AMBRE spectra computed with atmosphere models that have inconsistent [α/Fe] ratios.