Electrical resistivity and thermoelectric power of a quasi-one-dimensionalNb3Te4 single crystal inserted with mercury: HgxNb3Te4

The electrical resistivity and the thermoelectric power of Nb3Te4 inserted with mercury have been measured in the temperature range from 1.4 to 300 K. The magnitude of the resistivity and the residual-resistivity ratio are no t greatly affected by addition of Hg. The magnitude of the resistive anomal y at 90 K increases when adding a small amount of Hg but begins to decrease at about x = 0.03 and is no longer visible at about x = 0.15. Similarly, t he magnitude of the resistive anomaly at 30 K decreases with increasing Hg concentration and disappears at about x = 0.26. The thermoelectric power S also shows two anomalies at about 90 and 30 K. The anomaly of S at 90 K bec omes smeared by addition of Hg and disappears at about x = 0.3. The anomaly of 5 at 30 K becomes clear by addition of Hg and is still present at an am ount of x = 0.8. The sign of 5 is negative at all measured temperatures for x = 0.3 and is positive at temperatures below 7 K for x > 0.3. The superco nducting transition temperature is enhanced from 1.9 to 5.4 K by addition o f Hg. The upper critical fields parallel (H-c2 parallel to) and perpendicul ar (H-c2 perpendicular to) to the c axis have been measured near T-C. The c ritical fields show large anisotropy for x greater than or equal to 0.3: th e ratio H-c2 parallel to/H-c2 perpendicular to is about 5 for x < 0.3 and 4 0 for x greater than or equal to 0.3. These results are discussed on the ba sis of the multiband model with electron-like and hole-like carriers and wi th phonon drag.