I mean- not really? They have developed / synthesized the material, and they collaborated with another lab that had the skills and equipment to conduct and interpret specific experimental techniques and results.

Fairly common, especially in life sciences, and I suspect chemistry and materials science.

Added in edit: This doesn’t make the result any more or less credible; for that, the true test is independent replication of both the synthesis as well as the experimental measurements. But the fact that the two authors published two papers with different groups is orthogonal to whether the result is real / an experimental error / fraud. I so hope its true - but..lets wait for replication and validation by other qualified experts :)