  We experimentally study a broadband implementation of the atomic frequency
comb (AFC) rephasing protocol with a cryogenically cooled
Pr$^{3+}$:Y$_2$SiO$_5$ crystal. To allow for storage of broadband pulses, we
explore a novel regime where the input photonic bandwidth closely matches the
inhomogeneous broadening of the material $(\sim5\,\textrm{GHz})$, thereby
significantly exceeding the hyperfine ground and excited state splitting
$(\sim10\,\textrm{MHz})$. Through an investigation of different AFC preparation
parameters, we measure a maximum efficiency of $10\%$ after a rephasing time of
$12.5\,$ns. With a suboptimal AFC, we witness up to 12 rephased temporal modes.
