The Ni Curie temperature may explain it. The core temperature is what I am thinking about when I talk about the "coincidence" (understanding that we don't have direct read-outs from it). So if it is some sort of ferromagnetic transition phenomenon, then the close proximity to 100C of Ni's Curie temperature is, indeed, a coincidence/serendipity.
Now, the question is: Are we dealing with a ferromagnetic transition phenomenon???
Kim : http://www.physics.purdue.edu/people/faculty/yekim/BECNF-Ni-Hydrogen.pdf
specifically thinks it's the Curie temp.
His other papers referenced from that one are at : http://www.physics.purdue.edu/people/faculty/yekim.shtml
