Narrow range of the high-resolution, high signal-to-noise (S/N = 123 at 5800 Å) spectrum of KOI-2133 obtained with the CAFE échelle spectrograph at Calar Alto Observatory. We show the part of the spectrum used in determining the stellar metallicity (see Sect. 3.4.1) and mark with dotted lines the doublets used to estimate the effective temperature (see Sect. 3.4.2). The spectrum has been shifted to the rest frame by correcting for the barycentric velocity.