Blended feature around 670.78 nm for four K stars. Left: small region of the spectrum for two mid K stars with different rotation periods. Right: small region of the spectrum for two late K stars with different rotation periods. In both panels, the dashed black line shows the position of the Li doublet at 670.78 nm, while the dotted black line indicates the position of the Fe I line at 670.75 nm. Both features are blended independently of the spectral type and the rotation period of the star.