  We investigate interactions and ultracold collisions of high-spin but
spherical atoms with closed-shell atoms, focussing on the example of Cr with
Yb. Such a combination has only one potential energy curve but gives rise to a
substantial intra-atomic spin--spin interaction, which causes Feshbach
resonances due to rotationally excited states. We find such resonances are
guaranteed below 250 G and can reach widths of 10s of G in favorable
circumstances. We study the effect of hyperfine structure, which can create
additional wide resonances at low fields. Finally, we consider isotopic
substitution and show that for any realistic potential it is very likely at
least one combination of commonly used isotopes will have resonances with
experimentally favorable properties. Thus, this is a promising system for both
molecule formation and studying quantum mixtures including dipolar species.
