For Tamron as for Sigma, the lenses come in different flavours, one per system (Canon, Nikon, Olympus, Pentax).
Before selecting a lens, check carefully that the lens is compatible with your camera
Sometimes, there are differents systems for one brand. Pentax has normal DA lenses (the motor for the focus is in the camera) and SDM lenses (the motor for the focus is in the lens).
Have a look at that : 1 more connector on the outer metal ring and 2 more connectors on the inner dark ring. The screw head for focusing remains in the DA* SDM.
So check carefully
Pentax K-5 + BG4 + DA* 16-50 + DA* 50-135 + DA* 60-250 + AF-540FGZreivilophotography.weebly.com