Tunnel characteristics of partially gapped non-superconducting metals with charge- or spin-density waves

Current-voltage characteristics for symmetrical and non-symmetrical tunnel junctions involving non-superconducting partially dielectrized metals are calculated. Root singularities at eV = +/-Sigma and jumps at eV = +/- 2 Sigma, where V is the bias voltage, Sigma is the dielectric gap, and e is the elementary charge, are obtained for symmetrical junctions. For non-symmetrical ones current-voltage characteristics are non-symmetrical and depend on the sign of Sigma. The results obtained agree qualitatively with tunnel and point-contact measurements for layered dichalcogenides, NbSe3, and URu2Si2.