  Infrared emission bands with wavelengths between 3-20 {\mu}m are observed in
a variety of astrophysical environments [1,2]. They were discovered in the
1970s and are generally attributed to organic compounds [3,4]. However, over 40
years of research efforts still leave the source of these emission bands
largely unidentified [5-7]. Here, we report the first laboratory infrared (6-25
{\mu}m) spectra of gas-phase fullerene-metal complexes, [C60-Metal]+ (Metal =
Fe and V), and show with density functional theory calculations that complexes
of C60 with cosmically abundant metals, including Li, Na, K, Mg, Ca, Al, V, and
Fe, all have similar infrared spectral patterns. Comparison with observational
infrared spectra from several fullerene-rich planetary nebulae demonstrates a
strong positive linear cross-correlation. The infrared features of [C60-Metal]+
coincide with four bands attributed earlier to neutral C60 bands, and in
addition also with several to date unexplained bands. Abundance and collision
theory estimates furthermore indicate that [C60-Metal]+ could plausibly form
and survive in astrophysical environments. Hence, [C60-Metal]+ are proposed as
promising carriers, in supplement to C60, of astronomical infrared emission
bands, potentially representing the largest molecular species in space other
than the bare fullerenes C60, C60+, and C70. This work opens a new chapter for
studying cosmic fullerene species and carbon chemistry in the Universe.
