The demanded beam time for investigating [NH2(CH3)2]n[FeIIICuII(HCOO)6]n and [NH2(CH3)2]n[FeIIINiII(HCOO)6]n compounds, supported by basic and preliminary studies [ref.5 in the main text], represents the opportunity to characterize the magnetic structure using neutron diffraction below TN and refine the crystal structure in the paramagnetic phase. Fe(III)Ni(II) compound crystallize in the trigonal structure (P-31c space group) while Fe(III)Cu(II) compound crystallizes in the monoclinic structure (space group C2/c). The compounds exhibit ferrimagnetic order below 42 and 28.5 K respectively. To perform an accurate structural refinement in order to determine the hydrogen atoms we apply for 1 day of the high resolution D2B diffractometer. The magnetic structure determination will be carried out using the medium resolution and high flux D1B diffractormeter, to perform this task we will apply for 2 day of beam-time.