Left panel: comparison of with T_eff from interferometry of the Gaia Benchmark Stars (Heiter15). The red dashed line represents the offset. Right panel: relative temperatures as a function of [Fe/H]. The red line and the shade represent the trend and its scatter. The corresponding function and the errors ofits coefficients (in brackets) are shown in the legends. The cross symbol in both plots shows data points for μ Ara (HD 160691) that are considered as outliers.