I haven’t set up an ad hoc network… since forever but based on general principles and your screenshot,
I assume that the SSID should be the Workgroup name which has to be the same on every Host in your network. Are all your workgroups really called “mt”? This might be resolvable by simply using the “scan” button if another machine in your Workgroup is already setup. And, remember that NM is only configuring the wireless network connection, you should also be sure that your Workgroup is defined properly in your Network Settings in YAST.
Otherwise, if this is the first machine in your network, scroll down to
5.4.3. Configuring Your Wireless Card as an Access PointI’m not sure why this connection is described this way, to me if it’s truly an ad-hoc network the machine won’t behave like an AP. Am not sure why the vague caveats about preventing this kind of setup.
Although the Band and Channel settings could be left to Automatic, if you can I recommend setting them to known values.
All that said,
You should understand that Ad Hoc is generally ill-advised for a permanent basis. I would only set it up if I wanted to network to another machine once and likely never again. To set up a <permanent> and <reliable> wireless network, you should invest in an AP, even a very cheap one.