The large shear displacements of atomic layers in Gd-5(SixGe1-(x))(4) materials, coupled with the change of crystallographic symmetry and magnetic order, characterizes these transformations as magnetic-martensitic, which are extremely rare. The start and the end of the magnetic-martensitic transitions depends strongly on the direction of change (i.e., increasing or decreasing) of either or both the temperature and magnetic field. These profound bonding, structural, electronic, and magnetic changes, which occur in the Gd-5(SixGe1-(x)) system, bring about some extreme changes of the materials' behavior resulting in a rich variety of unusually powerful magneto-responsive properties, such as the giant magnetocaloric effect, colossal magnetostriction, and giant magnetoresistance.