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Title: Do megabar hydrides show consistent bulk magnetic evidence of superconductivity
Plain: Hydride samples are tiny and are enclosed in diamond cells, so measuring the magnetic field expulsion that defines a superconductor is hard, and some published magnetic data have been challenged.
Precise: For H3S and LaH10 at ~ 1.5 to 1.9 Mbar, establish bulk magnetic signatures (flux expulsion, trapped flux, penetration depth $\lambda_L$, critical current) that agree quantitatively with the resistive transitions and with the Ginzburg-Landau parameters implied by H_c2. An answer is a magnetic measurement reproduced by independent groups with consistent volume fraction and $\lambda_L$.
Settled by: Independent replication of magnetization or local magnetometry on H3S or LaH10 with quantitative agreement among volume fraction, $\lambda_L$ and H_c2.
Kind: well-posed
Answer type: yes-no
References: (empty)
Literature status: partially-resolved
Status note: Nitrogen-vacancy magnetometry imaging of flux expulsion in a cerium hydride (2024) and tunneling measurement of a gap near $60\,\mathrm{meV}$ in H3S (2025) support superconductivity; some magnetization data sets remain disputed.
Posed since: 2015