  Absolute dielectronic recombination (DR) rates for lithium-like
Ni$^{25+}$($1s^2 2s$) ions were measured at high-energy resolution at the
Heidelberg heavy-ion storage ring TSR. We studied the center-of-mass energy
range 0--130 eV which covers all $\Delta n$=0 core excitations. The influence
of external crossed electric (0--300 V/cm) and magnetic (41.8--80.1 mT) fields
was investigated. For the measurement at near-zero electric field resonance
energies and strengths are given for Rydberg levels up to n$=$32; also
Maxwellian plasma rate coefficients for the $\Delta n$=0 DR at electron
temperatures between 0.5 and 200 eV are provided. For increasing electric field
strength we find that for both the $2p_{1/2}$ and the $2p_{3/2}$ series of
Ni$^{24+}$($1s^2 2p_j n\ell$) Rydberg resonances with n>30 the DR rate
coefficient increases approximately linearly by up to a factor of 1.5. The
relative increase due to the applied electric field for Ni$^{25+}$ is
remarkably lower than that found in previous measurements with lighter
isoelectronic Si$^{11+}$, Cl$^{14+}$ and also Ti$^{19+}$ ions, [T. Bartsch et
al, Phys. Rev. Lett. {\bf 79}, 2233 (1997); {\bf 82}, 3779 (1999) and to be
published] and in contrast to the results for lighter ions no clear dependence
of the electric field enhancement on the magnetic field strength is found. The
Maxwellian plasma rate coefficients for $\Delta n$=0 DR of Ni$^{25+}$ are
enhanced by at most 11% in the presence of the strongest experimentally applied
fields.
