  High-spin yrast structures of even-even superheavy nuclei $^{254-258}$Rf are
investigated by means of total-Routhian-surface approach in three-dimensional
($\beta_2, \gamma, \beta_4$) space. The behavior in the moments of inertia of
$^{256}$Rf is well reproduced by our calculations, which is attributed to the
$j_{15/2}$ neutron rotation-alignment. The competition between rotationally
aligned $i_{13/2}$ proton and $j_{15/2}$ neutron is discussed. High-spin
predictions are also made for its neighboring isotopes $^{254,258}$Rf.
