[en] The synthesis, structure and microstructure of the IrSr₂TbCu₂O₈ cuprate showing metamagnetic properties are described. The sample was prepared at high temperatures and pressures up to 9.2 GPa. The structure is tetragonal, showing a 1212 type structure, that derives from the classical YBaCuO superconductor structure, replacing the tetracoordinated square planar copper [Cu-O₄] in the 'chains' by octahedral [Ir-O₆] groups that form a perovskite-like layer in the basal plane of the unit cell. A 'simple' cell, ∼a_pxa_px3a_p, where a_p is the basic perovskite unit cell parameter (a_p∼3.8 A), is supported by X-ray powder diffraction (XRD) and a so-called 'diagonal' one, ∼√2a_px√2a_px3a_p, by SAED; a microdomain texture of latter cell and a series of very interesting extended defects have been observed by HREM. Magnetic susceptibility measurements show a magnetic transition, T_N∼6 K, with negative Weiss temperature, that indicates antiferromagnetic interactions among the Tb moments. The magnetic structure has been determined by neutron diffraction. A detailed magnetic study has revealed a metamagnetic behavior, something not previously observed in this type of cuprates. Specific heat and resistivity measurements have also been performed to characterize the transition. - Graphical abstract: Reconstructed image from the SAED of the long c tetragonal axis (3a_p) of a IrSr₂TbCu₂O₈ crystal. A unit cell picture is included for comparison. Display Omitted