  We present study of derivatives of current-voltage I(V) characteristics of
point-contacts (PCs) based on Ba{1-x}Na{x}Fe2As2 (x=0.25) in the normal and
superconducting state. The detailed analysis of dV/dI(V) data (also given in
Appendix A) shows that the thermal regime, when temperature increases with a
voltage at a rate of about 1.8 K/mV, is realized in the investigated PCs at
least at high biases V above the superconducting (SC) gap \Delta. In this case,
specific resistivity \rho (T) in PC core is responsible for a peculiar dV/dI(V)
behavior, while a pronounced asymmetry of dV/dI(V) is caused by large value of
thermopower in this material. A reproducible zero-bias minima detected on
dV/dI(V) at low biases in the range \pm(6--9)mV well below the SC critical
temperature T_c could be connected with the manifestation of the SC gap \Delta.
Evaluation of these Andreev-reflection-like structures on dV/dI(V) points out
to the preferred value of 2\Delta/kT_c \approx 6. The expected second gap
features on dV/dI(V) are hard to resolve unambiguously, likely due to impurity
scattering, spatial inhomogeneity and transition to the mentioned thermal
regime as the bias further increases. Suggestions are made how to separate
spectroscopic features in dV/dI(V) from those caused by the thermal regime.
