  The superconducting fluctuations well inside the normal state of Fe-based
superconductors were experimentally studied through the in-plane
paraconductivity in several high-quality optimally-doped
BaFe$_{2-x}$Ni$_x$As$_2$ crystals. These measurements were performed in
magnetic fields with amplitudes up to 14 T, and different orientations relative
to the crystals c axis (0, 53 and 90 degrees). The results allowed a stringent
check of the applicability of a recently proposed Ginzburg-Landau approach for
the fluctuation electrical conductivity of 3D anisotropic materials in presence
of finite applied magnetic fields.
