NIR C i lines of iPTF13ebh in the two earliest spectra. The phase relative to the time of B maximum is labeled for each spectrum. The best-fit SYNAPPS models for both epochs yielded a velocity of 13 000  km s^-1 for C i, representing the base of the line-forming region. The best fit as a whole and the isolated contributions from the main ions responsible for the spectral features in each wavelength region are plotted. A vertical band marks this velocity for each C i line. C iλ1.4543 μm for iPTF13ebh is located near the region of strong telluric absorption, which is identified with an Earth symbol.