Same as Fig. 4 for typical metal-poor giant stars of the Galactic halo with two different α-enhancements. The main atmospheric parameters are T_eff = 4250 K, log(g) = 2.0, and [M/H] =  −1.5. Left panel: normalised spectra computed with only one line specy in the synthesis and assuming [α/Fe] = +0.0 as detected in halo giants probably originating from accreted dwarf galaxy satellites. Right panel: line blocking differences between the left panel case ([α/Fe] = +0.0) and a giant having [α/Fe] = +0.4 as measured in halo stars formed in-situ (see caption of Fig. 4, right panel).