Properties depend greatly on composition and fabrication process. Many properties are anisotropic due to the layered structure. Dirty samples, e.g., with oxides at the crystal boundaries, are different from clean samples.
*The highest superconducting transition temperature T is 39 K.
*MgB is a type-II superconductor, i.e. increasing magnetic field gradually penetrates into it.
*Maximum critical current (J) is: 10 A/m at 20 T, 10 A/m at 18 T, 10 A/m at 15 T, 10 A/m at 10 T, 10 A/m at 5 T.
*As of 2008 : Upper critical field (H): (parallel to ab planes) is ~14 T, (perpendicular to ab planes) ~3 T, in thin films up to 74 T, in fibers up to 55 T.