Co‐added spectra, grouped according to our derived CaT metallicity. Apart from the prominent CaT lines at 8498, 8542, and 8662 Å (right), there are a number of weaker lines (mostly Fe I), which become progressively stronger in the more metal‐rich spectra (the CaT line strength ΣW increases from 2.4 to 7.8 Å for the metallicity range covered in this figure). The co‐addition also emphasizes a few α‐element lines that become weaker for the more metal‐poor stars: note, for instance, the strong Ti I features at 8378, 8426, and 8435 Å.