The compound you are referring to, BiH5, is actually bismuth pentahydride. However, it appears that there may be a misunderstanding, as BiH5 is not a stable or well-characterized compound in the same way other hydrides are.
In terms of an "axe formula" or a molecular shape, if we were to hypothetically consider it as a valid molecule, one could assume the molecular geometry might be similar to that of other Group 15 hydrides like NH3 (ammonia) or PH3 (phosphine), which could lead to a pyramidal arrangement. However, without a stable compound to reference, we cannot definitively state its molecular geometry or provide an accurate depiction of its structure.
For practical usage, it's important to consult the latest scientific literature or databases for any newfound or theoretical compounds, as chemistry is an ever-evolving field.