  We consider the dynamics of relativistic spin-half particles in quantum
graphs with transparent branching points. The system is modeled by combining
the quantum graph concept with the one of transparent boundary conditions
applied to the Dirac equation on metric graphs. Within such an approach, we
derive simple constraints, which turn the usual Kirchhoff-type boundary
conditions at the vertex equivalent to the transparent ones. Our method is
applied to quantum star graph. An extension to more complicated graph
topologies is straightforward.
