H- and K-band stacked spectra of the SINFONI sample, divided into three subsets with log(L_IR/L_⊙)  <  11.35, 11.35  ≤  log(L_IR/L_⊙)  <  12, and log(L_IR/L_⊙)  ≥  12. The spectra are normalised to a linear fit of the continuum measured within the intervals [1.600, 1.610] μm and [1.690, 1.700] μm for the H band and [2.080, 2.115] μm and [2.172, 2.204] μm for the K band. From top to bottom, H-band and K-band spectra of the different subsets by increasing L_IR. The spectra are available in electronic form at the CDS.