  Recent experiments show CeMnNi$_{4}$ to have a nearly integer magnetic moment
and a relatively large transport spin polarization, as probed by Andreev
reflection, suggesting that the material is a half metal or close to it.
However, the calculations reported here show that it is not a half metal at
all, but rather a semimetal of an unusual nature. Phonon properties should also
be quite unusual, with rattling low-frequency Mn modes. Nontrivial transport
properties, including a large thermolectric figure of merit, $ZT,$ are
predicted in the ferromagnetic state of the well ordered stoichiometric
CeMnNi$_{4}$
