A 3 to 1 Ni/Si antiferromagnetic layered phyllosilicate, Ni3Si(C3H6NH3)F0.65O1.9(OH)(4.45)(CH3COO)(1.1)center dot xH(2)O, was modified with K-4[Fe(CN)(6)]center dot 3H(2)O. This compound retained its ordering as proved by X-ray diffraction, while infrared spectra revealed the presence of [Fe(CN)(6)](4-) groups and X-ray photoelectron spectroscopy showed that the latter partially substitute the acetate groups. Both the parent and the modified compound are canted antiferromagnets with an anisotropy perpendicular to the layers and show spin-flop transitions. For the parent compound, a single step spin-flop occurs at H = 24 kOe. The modified compound shows increased antiferromagnetic canting and a two-step transition (H-1 = 24 kOe, H-2 = 48 kOe). These results testify to the existence of competing interactions that depend sensitively on the grafted species.