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The point contact Andreev reflection employing niobium tips was used to determine the degree of transport current spin polarization ͑P t ͒ at the free surface of bulk NiMnSb at 4.2 K. The data was analyzed within the framework of a modified version of the Blonder, Tinkham, and Klapwijk formulism taking into account the two spin polarized channels in the ferromagnet and treating the interface as a planar delta function barrier of height Z between free electron materials. We find that the measured spin polarization is rather insensitive to different surface preparations and magnetic domain structure, and the maximal value of the P t at Z = 0 is 44%, consistent with recent calculations of the surface reconstruction of NiMnSb. Saturation magnetization of the samples was found to be 3.6 B per formula unit indicative of a small amount of atomic disorder.

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