Muon radiative energy loss (in 1.0E06 cm^2/g) in potassium (K) with Z = 19, A = 39.0983(1) (f12.0,4f12.4) E (GeV) b_brem b_pair b_nucl b_total 2. 0.6576 0.3103 0.4250 1.3929 5. 0.8951 0.7624 0.4531 2.1106 10. 1.0879 1.1212 0.4423 2.6514 20. 1.2869 1.4973 0.4243 3.2086 50. 1.5507 2.0345 0.4044 3.9896 100. 1.7419 2.4048 0.3947 4.5414 200. 1.9203 2.7457 0.3899 5.0559 500. 2.1269 3.0718 0.3895 5.5882 1000. 2.2557 3.2511 0.3957 5.9026 2000. 2.3594 3.3834 0.4059 6.1487 5000. 2.4594 3.4958 0.4246 6.3798 10000. 2.5108 3.5486 0.4434 6.5028 20000. 2.5471 3.5829 0.4653 6.5953 50000. 2.5753 3.6092 0.4996 6.6840 100000. 2.5890 3.6202 0.5289 6.7380