A note on the reliability of superconducting material databases and the report of the absence of superconductivity in the Mn5Si3-type Zr5Ga3 compound

Here, we report the synthesis and characterization of the Zr5Ga3 intermetallic phase listed as a superconductor with Tc = 3.85 K by multiple sources and included in the Supercon database. We show that the Mn5Si3-type hexagonal Zr5Ga3 compound reveals no superconducting transition down to T = 1.9 K. We describe possible sources of false positive reports of superconductivity in the literature and how they affect the reliability of superconducting materials databases, such as Supercon and Supercon2. Several examples of erroneous and suspicious reports are considered. We also discuss how the presence of spurious entries in material databases can hamper machine learning studies aimed at the discovery of novel superconductors. Our conclusions call for high-quality, curated material property databases, show the value of research on new superconducting materials, and highlight the importance of publishing negative results.