Structural, transport, and superconducting properties of Ir-doped Nb2− <i>x</i> Ir <i>x</i> PdSe5

We present a systematic study of the structural, normal-state transport, and superconducting properties of Ir-doped Nb2PdSe5 with nominal composition Nb2−xIrxPdSe5. Powder x-ray diffraction confirms that Ir incorporation preserves the host crystal structure without secondary phases up to x = 0.10, indicating successful substitution at the Nb site. Electrical resistivity measurements (ρ–T) show metallic behavior in the normal state. As Ir content increases, the superconducting transition temperature (Tc) decreases monotonically, accompanied by an increase in residual resistivity, suggesting enhanced impurity scattering. Low-temperature resistivity exhibits a near-quadratic temperature dependence, consistent with dominant electron–electron scattering in the normal state. Magnetization measurements confirm bulk superconductivity and show a systematic decrease in the superconducting volume fraction with increasing doping. The upper critical field (Bc2) evolves with Ir substitution, reflecting the interplay among disorder, spin–orbit coupling, and superconducting pair-breaking effects. The suppression of Tc with increasing x indicates that Ir substitution primarily introduces scattering-induced pair weakening rather than favorable electronic tuning. Hall coefficients RH and resistivity ρxy indicate a reduction in carrier density with Ir substitution in Nb2−xIrxPdSe5. These results clarify the role of chemical substitution and disorder in governing superconductivity in quasi-one-dimensional chalcogenide systems.