Radiative recombination (inverse photoionization) is believed to be well un
derstood since the beginning of quantum mechanics. Still, modern experiment
s consistently reveal excess recombination rates at very low electron-ion c
enter-of-mass energies. In a detailed study on recombination of F and C ion
s with magnetically guided electrons we explored the yet unexplained rate e
nhancement, its dependence on the magnetic field B, the electron density n(
e), and the beam temperatures T-perpendicular to and T-parallel to. The exc
ess scales as T-perpendicular to(-1/2) and, surprisingly, as T-parallel to(
-1/2), increases strongly with B, and is insensitive to n(e). This puts str
ong constraints on explanations of the enhancement.