Last year's Nobel Prize in Chemistry honored the discovery that certain organic polymers¿plastics¿conduct electricity almost as well as metals. Now researchers from the U.S., Germany and Switzerland have gone one step further: in this week's issue of Nature, they report the first superconducting organic plastic¿one that conducts electricity with no resistance.

They cast a thin film of a polythiophene-type plastic and found that it becomes superconducting below a temperature of 2.5 K, fairly close to absolute zero. Instead of chemically doping the material¿a step normally required to turn a plastic into a good conductor¿they injected it with charge carriers (electrons or holes) using a field-effect transistor. Also of importance, the polymers in the film form well-ordered nanocrystals.

Plastics are much cheaper to produce than metals, making them an interesting alternative to conventional superconductors. The temperature they need to be cooled down to, however, is very low, at least for now.

Just a week ago and also in Nature, Japanese researchers reported a new high-temperature superconductor. They found that magnesium diboride (MgB2) can become superconducting at 39 K, much warmer than any other metal-containing superconductor. An article from U.S. and French researchers in today's Science explores the properties of MgB2 further: it seems to behave partly as a metal and partly as a ceramic superconductor.

Physicists are very excited about MgB2: the American Physical Society meeting in Seattle next week devotes a whole session to this old compound and its newly discovered property, including more than 65 papers.