AFEK 2021 search for millicharged particles bound to matter using an optomechanical device. No signal was observed. Limits placed in the abundance vs. charge plane (Fig. 3). This is translated to the mass versus charge plane by requiring bound states to be stable.
JAVORSEK 2001B search for (neutral) SIMPs (strongly interacting massive particles) bound to Au and Fe nuclei from various origins with exposures on the earth's surface, in a satellite, heavy ion collisions, etc. Here $\mathit M$ is the mass of the anomalous nucleus. See also JAVORSEK 2002 .