  By using our novel Grassmann formulation we study the phase transition of the
spanning-hyperforest model of the k-uniform complete hypergraph for any k>= 2.
The case k=2 reduces to the spanning-forest model on the complete graph.
Different k are studied at once by using a microcanonical ensemble in which the
number of hyperforests is fixed. The low-temperature phase is characterized by
the appearance of a giant hyperforest. The phase transition occurs when the
number of hyperforests is a fraction (k-1)/k of the total number of vertices.
The behaviour at criticality is also studied by means of the coalescence of two
saddle points. As the Grassmann formulation exhibits a global supersymmetry we
show that the phase transition is second order and is associated to
supersymmetry breaking and we explore the pure thermodynamical phase at low
temperature by introducing an explicit breaking field.
