*Dislocations have been associated with the filamentary structure proposed as a mixed-state structure capable of producing plastic deformation effects observed in superconducting propenties. The local enhancement of critical field about a dislocation due to its elastic strain field was calculated, together with the magnitude (from thermodynamic considerations) of the critical field necessary to form a filament in a parallel external magnetic field equal to the bulk critical field. The actual dislocation structure in Ta was also examined by transmission electron microscopy. The results indicate that the propenties of highcritical-current, high-critical-field superconductors can be improved by forming an interconnected network of material having a locally attenuated electron mean free path.
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