  Diamond is an electrical insulator in its natural form. However, when doped
with boron above a critical level (~0.25 at.%) it can be rendered
superconducting at low temperatures with high critical fields. Here we present
the realization of a micrometer scale superconducting quantum interference
device $\mu$-SQUID made from nanocrystalline boron doped diamond (BDD) films.
Our results demonstrate that $\mu$-SQUIDs made from superconducting diamond can
be operated in magnetic fields as large as 4T independent on the field
direction. This is a decisive step towards the detection of quantum motion in a
diamond based nanomechanical oscillator.
