S.D. Codified Laws § 5-18A-8
A contract may be awarded for supplies or services without competition if the purchasing agency determines in writing that the supplies or services are of such a unique nature that the contractor selected is clearly and justifiably the only practicable source to provide the supplies or services. The determination that the contractor selected is justifiably the sole source shall be based on either the uniqueness of the supplies or services or the sole availability at the location required. In such cases, the purchasing agency shall conduct negotiations, including price, delivery, and quantity to obtain the most advantageous price and shall include the written verification of the sole source in the contract file. This section does not apply to construction services or construction equipment.
SDCL 5-18A-8