Here's why:

* Semiconductor: Tellurium is a semiconductor, meaning it has a conductivity between that of a conductor and an insulator.

* Low Thermal Conductivity: Semiconductors generally have lower thermal conductivity compared to metals.

* Crystal Structure: Tellurium's crystal structure contributes to its low thermal conductivity.

While tellurium does conduct heat, it's not a very good conductor compared to metals like copper or silver.