Anomalous Properties of Single Crystal Niobium*

A number of anomalous properties have been observed in niobium over the years. The most striking, perhaps, is the anisotropic upper critical field, H$_{c2}$, in the superconducting state. Nb has also been observed to exhibit a ``peak effect,'' a peak in the critical current near T$_{c}$. Experimental evidence will be presented that identifies the source of some of these anomalies as due to interstitial hydrogen at concentrations of a few percent. Thermal expansion, specific heat, resistivity versus temperature, and other data will be presented.