<p>Solid oxide fuel cells (SOFCs) receive significant attention due to theirs high efficiency, environmental advantages, and fuel flexibility. The interconnect is a crucial part that connects each cell in the SOFC stack. The High Entropy Alloy (HEA) of FeCoCrNiMn_0.5 is a promising candidate for an interconnect material at intermediate temperatures (600&#xa0;°C to 800&#xa0;°C) in Solid Oxide Fuel Cells (SOFC) due to its good thermal stability and electrical conductivity. However, FeCoCrNiMn_0.5 HEA has a higher coefficient of thermal expansion (CTE) than the other interconnect materials (SUS 430, Crofer 22 APU) in SOFCs such as LSM (Lanthanum Strontium Manganite) cathode and NiO-YSZ anode. The high CTE in an HEA is undesirable as it mismatches with the CTE of cathodes and anodes in SOFC. The present study investigates the thermophysical properties and oxidation behavior of an Nb-contained HEA (Cr₂₁Co₂₁Fe₂₁Ni₂₁Mn₁₁Nb₅) to achieve reduced CTE and improved oxidation properties than the existing interconnect HEAs. The novel Cr₂₁Co₂₁Fe₂₁Ni₂₁Mn₁₁Nb₅ HEA was produced by the vacuum arc melting technique. The structure, chemical composition, mechanical properties, CTE, and thermal stability of the HEA were investigated. The oxidation study was also carried out by oxidizing the as-cast HEA at 800&#xa0;°C for 25, 50, 100, and 200 hours. The study revealed that the presence of Nb reduces the CTE, increases oxidation resistance, and improves the mechanical properties of the HEA. The harmful Chromium oxide layer does not appear on the top of the thermally grown oxide layer during oxidation of the HEA. This passivation of the Chromium oxide layer will significantly reduce the Cr-poisoning in SOFC.</p>