The valve (10) has a seat valve (27) comprising a hollow cone-shaped valve seat (24) and an hemispherical shutoff element (26). An afflux bore (23) having contact with a pressure-medium inlet (19) discharges centrically into the valve seat (24). A solenoid armature (30) acting upon the seat valve (27) in opening fashion grips a push rod (25) comprising the shutoff element (26). The solenoid armature cooperates with a pole body (42) according to the flat-type armature principle. A preloaded return spring (39) acting on the seat valve (27) in closing fashion is arranged between the pole body (42) and the solenoid armature (30). The valve (10) works as a proportioning valve, because, in addition to a suitable design of the seat valve (27) and push rod (25), the magnetic force is infinitely variable and, together with a hydraulic force, has a monotonously increasing course as the valve opening stroke increases, while the spring force—which also has a monotonously increasing course as the valve opening stroke increases—has a positive slope that is greater than that of the course of the magnetic and hydraulic force.