  A plethora of temperature induced phase transitions have been observed in
$[CH_3NH_3][M(HCOO)_3]$ compounds, where M is Co(II) or Ni(II). Among them, the
nickel compound exhibits a combination of magnetic and nuclear
incommensurabil-ity below N\'eel temperature. Despite the fact that the
zero-field behavior has been previously addressed, here we study in depth the
macroscopic magnetic behavior of this compound to unveil the origin of the
atypical magnetic response found in it and in its parent family of formate
perovskites. In particular, they show a puzzling magnetization reversal in the
curves measured starting from low temperatures, after cooling under zero field.
The first atypical phenomena is the im-possibility of reaching zero
magnetization, even by nullifying the applied external field and even
compensating it for the influence earth's magnetic field. Relatively large
magnetic fields are needed to switch the magnetization from negative to
positive values or vice versa, which is compatible with a soft-ferromagnetic
system. The atypical path found in its first magnetization curve and hysteresis
loop at low temperatures is the most noticeable feature. The magnetization
curve switches from more than 1200 Oe from the first magnetization loop to the
subsequent magnetization loops. A feature that cannot be explained using a
model based on unbalanced pair of domains. As a result, we decipher this
behavior in light of the incommensurate structure of this material. We propose,
in particular, that the applied magnetic field induces a mag-netic phase
transition from a magnetically incommensurate structure to a magnetically
commensurate structure.
