I doubt there's any effort at all going into keeping the share prices in sync or tandem. The market will naturally keep the prices sync'ed.
The market is valuing SLR on the combined assets of both companies. IGR shares will be converted into SLR shares when the merger is finalised, at the ratio of one SLR share for every 6.28 IGR shares held.
As soon as the IGR shares sell at a discount to the above ratio, they will be bought because they are providing a cheap discounted entry into SLR.
At the moment the shares are selling around a 1 to 2cent discount to the ratio. This probably reflects the added risk that the merger may not go ahead.
IGR Price at posting:
60.5¢ Sentiment: Buy Disclosure: Held