We are interested in understanding what is the area of the graph of a map u with vector values (in particular, from the plane to the plane) in the case when u is discontinuous.  We will concentrate on a very special case, of a function u taking three vectors (at the vertices of an equilateral triangle) and jumping on a triple junction with angles at 120 degrees.  This problem, related to a question posed by De Giorgi several years ago, is strictly related to minimal surfaces with codimension two.