  Over the past six years, superconductivity at high temperatures has been
reported in a variety of hydrogen-rich compounds under high pressure. That
high-temperature superconductivity should exist in these materials is expected
according to the conventional theory of superconductivity, as shown by detailed
calculations. However here we argue that experimental observations rule out
conventional superconductivity in these materials. Our results indicate that
either these materials are unconventional superconductors of a novel kind,
which we term `nonstandard superconductors', or alternatively that they are not
superconductors. If the former, we point out that the critical current in these
materials should be five orders of magnitude larger than in standard
superconductors, potentially opening up the way to important technological
applications. If the latter, which we believe is more likely, we suggest that
the signals interpreted as superconductivity are either experimental artifacts
or they signal other interesting physics but not superconductivity.
