Left panel: montage of X-Shooter spectra at the Nai wavelength; the orbital phase corresponding to each spectrum is marked on the right side of the figure. The vertical dashed line marks the rest wavelength of the doublet, while the cyan-shaded area marks the drift observed in U Sco and the telluric spectra. Central panel: montage of X-Shooter spectra at the Caii wavelength. The vertical dashed lines marks the doublet rest wavelengths. Right panel: selected portions of the July 2011 U Sco spectrum showing the secondary star absorption features: the G band at  ~4300 Å (top), and the Mg i triplet (bottom).