Dataset associated with 'On the Origin of Superconductivity at Nickel-Bismuth Interfaces'

Unconventional superconductivity has been suggested to be present at the interface between bismuth and nickel in thin-film bilayers. In this work, we study the structural, magnetic and superconducting properties of sputter deposited Bi/Ni bilayers. As-grown, our films do not display a superconducting transition, however, when stored at room temperature, after about 14 days our bilayers develop a superconducting transition up to 3.8 K. To systematically study the effect of low temperature annealing on our bilayers, we perform structural characterization with X-ray diffraction and polarized neutron reflectometry, along with magnetometry and low temperature electrical transport measurements on samples annealed at 70C. We show that the onset of superconductivity in our samples is coincident with the formation of ordered NiBi_3 intermetallic alloy, a known $s$-wave superconductor. We calculate that the annealing process has an activation energy of (0.86+/- 0.06)eV. As a consequence, gentle heating of the bilayers will cause formation of the superconducting \NiBi\ at the Ni/Bi interface, which poses a challenge to studying any distinct properties of Bi/Ni bilayers without degrading that interface.