The Dunkl-Dirac operator is a deformation of the Dirac operator by means of Dunkl derivatives. We investigate its symmetry algebra generated by elements supercommuting with the Dunkl-Dirac operator. This symmetry algebra is realised inside the tensor product of a Clifford algebra and a rational Cherednik algebra associated with a reflection group or root system. For reducible root systems of rank three, we determine all the irreducible finite-dimensional representations and conditions for unitarity. Polynomial solutions of the Dunkl-Dirac equation are given as a realisation of one family of such irreducible unitary representations. CONTENTS 1. Introduction 2. The dihedral Dunkl-Dirac equation 2.1. The Dunkl-Laplace and Dunkl-Dirac operators 2.2. The dihedral Dunkl operators 3. The symmetry algebra of the Dunkl-Dirac operator 3.1. General symmetry algebra for 3D space 3.2. Dihedral 3D symmetry algebra and ladder operators 3.3. Unitary structure 4. Finite-dimensional irreducible representations 4.1. Preliminary general results and idea of the proofs 4.2. Proof of Theorem 4.1 4.3. Proof of Theorem 4.2 5. The monogenic representations 6. Concluding remarks Acknowledgements References Appendix A. Double coverings A.1. Irreducible representations for the odd case A.2. Irreducible representations for the even case