The doping effect of zirconium on the structure, Seebeck coefficient and electrical resistivity of -rhombohedral B was studied for the metal rich concentration range ZrxB100-x, 1.88x2.75. Structural studies proved the Zr atoms mainly in E and D voids for the metal rich compositions, and also elucidated the minor Zr occupancies of the N, F and A1 holes. Seebeck coefficients were effectively shifted within a wide range of positive and negative values by varying the Zr content (p-type: Smax +420 VK-1 at 673 K for x=1.88; n-type: Smax -670 VK-1 at 473 K for x=2.74). Electrical resistivities generally followed the Motts relation for the variable-range hopping. Excellent compositional agreement has been observed between structural and thermoelectric properties discontinuities.