Enhanced non-metallic behavior on the verge of magnetic instability in Fe2V1−xNbxAl Heusler alloys

► Present study on Fe2V1−xNbxAl show that lattice expansion takes place on increasing Nb. ► Experimental results are consistent with predicted trends from band structure calculation. ► It is shown that the lattice expansion plays a role in observed unusual physical properties. ► Analysis of magnetic data confirms the presence of magnetic clusters (site disorder). ► Finally we show that the magnetic and electrical properties are interrelated.